The treatment of a CATHARANTHUS ROSEUS cell suspension culture with a low concentration of PYTHIUM elicitor stimulated the alkaloid production. When these pretreated cells were resuspended in a medium that did not contain the fungal extract, the positive effects of the treatment on alkaloid synthesis and excretion were lost and, moreover, the standard level of production was not recovered. A second treatment of these cells with PYTHIUM elicitor at day 5 of the second culture cycle greatly impaired growth kinetics, but did not stimulate the alkaloid production observed with standard cultures. Repeated treatments with a low concentration of fungal elicitor seemed to have a negative long-term effect on both growth and alkaloid synthesis and did not appear to be a useful process for production purposes.