A series of analogues of diacylglycerol has been prepared and tested as inhibitors of protein kinase C (PKC). The diketone analogues, 10-hydroxymethyl-8,13-eicosanedione (24), 10-acetoxymethyl-8,13-eicosanedione (25), and 10-methoxymethyl-8,13-eicosanedione (26) each inhibited PKC activated by 2-0-acetyl-1-0-oleoylglycerol. Compound 24 was the most effective inhibitor of the growth of MR4 and HT29 cells in culture, and 26 was more effective than 24 against HL60 cells.