A number of benzophenanthridine alkaloids are induced in suspension cultures of Eschscholtzia californica after treatment with an elicitor prepared from yeast extract. The formation of the alkaloids sanguinarine, chelerythrine and macarpine has been studied in relation to; elicitor concentration, incubation time after elicitation, and culture age. A significant portion of these alkaloids is released into the medium. Sanguinarine and chelerythrine reach maximum levels a few hours after the time of elicitation. Thereafter, their levels decline and the amount of macarpine increases. Viability of elicited cells, as determined by their subsequent growth, is not significantly reduced. There is a good correlation between induced tyrosine decarboxylase activity and alkaloid formation.