IN a commercial for Trojan condoms that has its premiere tonight, women in a bar are surrounded by anthropomorphized, cellphone-toting pigs. One shuffles to the men’s room, where, after procuring a condom from a vending machine, he is transformed into a head-turner in his 20s. When he returns to the bar, a fetching blond who had been indifferent now smiles at him invitingly.

Directed by Phil Joanou (“State of Grace”), with special effects by the Stan Winston Studio (“Jurassic Park”), the commercial is entertaining. But it also has a message, spelled out at the end: “Evolve. Use a condom every time.”

“We have to change the perception that carrying a condom for women or men is a sign they’re on the prowl and just want to have sex,” said Linda Kaplan Thaler, chief executive of the Kaplan Thaler Group, the New York advertising agency that created the “Evolve” campaign. “It’s a sign of somebody being prepared — if the opportunity arises — to think about their own health and the health and safety of their partner.”

But the pigs did not fly at two of the four networks where Trojan tried to place the ad.

Fox and CBS both rejected the commercial. Both had accepted Trojan’s previous campaign, which urged condom use because of the possibility that a partner might be H.I.V.-positive, perhaps unknowingly. A 2001 report about condom advertising by the Henry J. Kaiser Family Foundation found that, “Some networks draw a strong line between messages about disease prevention — which may be allowed — and those about pregnancy prevention, which may be considered controversial for religious and moral reasons.”