Vindoline concentrations in the leaves of 70 Catharanthus Roseus of 3 cultivars were analyzed by HPLC, and 3 plants were selected for starting callus cultures on different media. When the initial calli were analyzed using a vindoline-specific RIA, the assay suggested a vindoline content of about 10 (-5)% dry weight for one-third of the first 60 cultures examined. Due to the unexpectedly high incidence of vindoline-positive calli, the screening programme was discontinued and efforts were concentrated on verifying the existence of this alkaloid in the cells. Suspension cultures derived from the 5 most immunopositive calli in an alkaloid production medium were analyzed by HPLC and GC/MS. Comparison with reference material showed that the heterotrophic suspension cultures contained a compound identical to vindoline.