A Catharanthus roseus cell line was characterized for the accumulation of secologanin, tryptophan, tryptamine, strictosidine and ajmalicine, as well as for the activities of the enzymes geraniol 10-hydroxylase, tryptophan decarboxylase and strictosidine synthase. The effects of the inoculum size on these parameters were discussed. The increase of the inoculum size from 40–160 g of fresh weight per liter of medium favored the accumulation of secologanin and alkaloids. A coordinated regulation of geraniol 10-hydroxylase and tryptophan decarboxylase by inoculum size seems to contribute to the effects observed.