Kath reportedly had a history of using alcohol and other drugs, including cocaine. Chicago bandmates have indicated that he was also increasingly unhappy. Bassist Peter Cetera said that Kath would have been the first to quit Chicago had he lived, and producer James William Guercio has said that Kath was working on a solo album before he died. Former drummer Danny Seraphine mentions in his autobiography "Street Player: My Chicago Story" that Kath had a high tolerance for drugs.
Around 5 p.m., on January 23, 1978, after a party at roadie/band technician Don Johnson's home in Woodland Hills, Los Angeles, California, Kath took an unloaded .38 revolver and put it to his head, pulling the trigger several times on the empty chambers. Johnson had warned Kath several times to be careful. Kath then picked up a semiautomatic 9 mm pistol and, leaning back in a chair, said to Johnson, "Don't worry, it's not loaded". After showing the empty magazine to Johnson, Kath replaced the magazine in the gun, put the gun to his temple, and pulled the trigger. There was a round in the chamber, and he died instantly. It was the week before his 32nd birthday.