Previous studies have shown that prostaglandin E(2) (PGE(2)) and vitamin E succinate can act in an additive manner to inhibit the proliferation of human oral squamous carcinoma cells (SCC-25), The initial studies on the additive anticancer activity of PGE(2) and vitamin E succinate have been extended to include antineoplastic PGs, Delta(12)-PGJ(2) and PGJ(2). Treatment of oral squamous carcinoma cells (SCC-15) with Delta(12)-PGJ(2), PGJ(2), and vitamin E succinate, individually, caused significant concentration-dependent inhibition of cell proliferation to various degrees, PGJ(2) was most potent and caused an inhibition that corresponded to 85.55% at 10(-5) M. Addition of 1 mu M of vitamin E succinate to Delta(12)-PGJ(2) or PGJ(2) resulted in a significant increase in the inhibitory potency of the lower concentrations of the two PGs. These results suggest a novel role for a mixture of PGs and vitamin E as potent antitumor proliferative agents.