Suspensions of Walker and HeLa cells, rat fibroblasts and human stimulated lymphocytes were incubated over various periods with the synthetic amino steroid, 2 beta,16 beta-dipiperidino-5 alpha-androstane-3 alpha,17 beta-diol dipivalate (DAP). The acute cell destroying effect was found to be exponentially time and dose dependent within a certain range. With lower nontoxic doses, decreases in the mitotic and labelling indices were observed, and clotted mitotic figures occurred. The effects were essentially the same for all experimental cell types; chromosome alterations were not seen.