During the filming of his last Perry Mason movie in the spring of 1993, Burr fell ill. A Viacom spokesperson told the media that the illness might be related to the renal cell carcinoma (malignant kidney tumor) that had been removed from Burr that February. It was determined that the cancer had spread to his liver and was at that point inoperable. Burr threw several "goodbye parties" before his death on September 12, 1993, at his Sonoma County ranch near Healdsburg. He was 76 years old.