Jeffrey T. Porcaro, a rock musician who played drums for Sonny and Cher, Bruce Springsteen and the Grammy Award-winning group Toto, died on Wednesday in Los Angeles. He was 38 years old.

His manager, Larry Fitzgerald, said it was believed that he died of cardiac arrest, possibly from an allergic reaction to pesticides. Autopsy results are awaited, said a spokesman for Humana Hospital West Hills in Los Angeles.

Mr. Porcaro collapsed while spraying pesticides in the garden at his home in Hidden Hills, a Los Angeles suburb. He was taken to Humana Hospital, where he was pronounced dead.

Mr. Porcaro was a sought-after studio musician who performed on recordings for such stars as Paul Simon, Boz Scaggs, Joe Cocker, Steely Dan, Seals and Crofts, Hoyt Axton and Mr. Springsteen, with whom he recorded the "Human Touch" album released this year. On the Road