In theater as in other forms of retail, you have to advertise. But declaring your show a comedy right there in the title is like issuing a challenge, and you'd better back it up by actually being funny.

If you think about it, Shakespeare, the co-owner of an acting company with a financial interest in marketing, had a fondness for in-your-face comic titles, such as "As You Like It" or "Much Ado About Nothing." But no title is bolder than "The Comedy of Errors," which is pretty much like saying, "the comedy of comedy," since errors (in the sense of comic confusion and cross-purposes) are the comic writer's chief stock in trade.

The Public Theater and director Ted Pappas are very aware of this, so, for its colorful, elaborate season-opening staging of Shakespeare's short knock-about farce, they work hard to live up to the title. Maybe too hard -- the comic shtick of the early scenes feels forced. It takes a long time to get the momentum going, but when it does, it doesn't seem to have taken so long after all.

Doubtless this labored beginning is the defect of the production's virtue, its clarity. Every actor seems determined to have every word register clearly, which is fine, except when carried to excess with such high volume that it seems like declamation. Probably they don't trust our ability to understand the 400-year-old language and perhaps that's wise, but in the earliest scenes, the actors are shouting at each other.

The show's comic bones, though, are solid -- characterization, blocking, comic detail -- and the Public's designers provide a set (more about this later) that is a play in itself, or at least a joking quiz on the Shakespearean canon. All this well-drilled production still needs to do is relax, let in some air and indulge its sense of play.

Shakespeare ups the ante at the start with a long speech in which a merchant of Syracuse, condemned to die by Duke Solinus because this is Ephesus and there's a trade war, explains that he's searching for his identical twins, separated at birth, and their slaves, identical twins of the same age. Pappas helps us through the exposition by showing the Duke and his Keystone Kops gravitate from boredom to sympathy; he could also make it clear the merchant spins out the tale as a way of postponing sentence.

That business taken care of, we meet one pair of twins, Antipholus of Syracuse and his slave Dromio (both also just arrived), who can't figure out why everyone seems to know them, especially the women who claim them as husbands. This everyone includes an urban gallery of merchants, goldsmith, prostitute and cops. Fortunately, Mrs. Antipholus (of Ephesus) has a comely sister, so we know that the other Antipholus will be well mated, and even more fortunately Mrs. Dromio does not, so the other Dromio will be spared.

The play finally gathers critical comic mass pretty far through Act 1, when the visiting Antipholus shocks Luciana, who supposes herself his sister-in-law, with an avowal of love, and his Dromio performs bawdy geographical shtick about all the countries that might be discovered in the fat kitchen wench who claims to be his wife.

Act 2 picks up pretty much where that left off and the ultimate chase and recognition scene, which is what the entire play has been laboring to set up, is long and enjoyable.

If you do find yourself with a few minutes to fill, you can curl up with James Noone's witty set, which turns Ephesus into an urban street scene somewhat like Boston's North End or Pittsburgh's Bloomfield. Every shop front, billboard or street sign -- and there are about four dozen -- makes punning and allusive use of names from Shakespeare's plays or life and times: Prospero's House of Magic; Cleopatra's Falafel; Duncan Donuts; Christopher Marlowe, private detective; Gloucester & Sons Opticals (a gruesome joke); or "Fortin Bras & Lingerie" (a personal favorite).

Antipholus' house, The Phoenix, becomes a colorful Italian restaurant. That begs the question of just when they carry on this business, unmentioned in the script. But you can't expect the set to make literal sense, as when someone announces they're heading to the Phoenix and then marches offstage. We always have to accept a slight disjunction in these clever modernizings: for example, the Dromios are called servants, not slaves, and all the slapping around they get is accompanied with cartoony noises.

The setting works well to inform the supporting characters, justifying Solinus' Godfather-like lilt, a cop's Oirish accent and the Prostitute's gum-snapping "Guys and Dolls" attitude.

The comic stars, as they should be, are the Dromios, Tom Ford and Nat DeWolf. Among many comic bits, those that appealed to me include Tom Schaller's suave Solinus; Doug Pona's southern merchant, looking like Don King playing Col. Sanders; Lisa Ann Goldsmith's Prostitute, picking lint out of her decolletage; Marcus Stevens' short scene played in Italian; and Pappas' ingenious way of bringing "swords" into a contemporary setting.

In the serious plot of the Antipholuses (Antipholi?), Darren Elikir scores with the Syracusean's romantic bewilderment. Doug Mertz is too limited to a perpetual scowl as his Ephesan twin -- we should see some of his charm, too. That would bring a little light into the life of his wife, Adriana, played with comic skill by Helena Ruoti. Amy Landis is fetching as the unmarried sister who has the temerity to lecture Adriana on marital politics.

The serious theme in "Comedy of Errors" is all about loss of identity, an issue raised by twins and traveling. The fear of losing your sense of self gives "Comedy of Errors" a solid base that makes it more than just slapstick, justifying its status as a comedy in the deeper, structural sense of threat followed by rejuvenation, leading to a happy ending that goes deeper than laughter.

But that's for us to feel, not the actors, who are too ready to seem cast in marble as it is. From them, we want more sense of spontaneous life. I bet it will come.

"The Comedy of Errors" continues at Pittsburgh Public Theater at O'Reilly Theater, 621 Penn Ave., Downtown, through Nov. 4; Tues.-Fri. 8 p.m.; Sat. 2 and 8 p.m.; Sun. 2 and 7 p.m.; several exceptions. Tickets: $15-$53; 412-316-1600.