N-(N'-Phenethylthiocarbamoyl) derivatives of sphingosine and sphinganine were prepared. They had antitumour activity: GC50 values of 0.64+/-0.02 microM (N = 18) and 1.6+/-0.01 microM (N = 18). respectively, with human leukaemia 60 cells in vitro. This antitumour effect may contribute to the suppression of carcinogenesis associated with dietary phenethyl isothiocyanate and sphingolipid bases.