Crocus sativus cell suspension culture converted crocetin into several glycosyl esters when the culture was fed with the encapsulated substrate. Glycosylated pigments were stored in vacuoles. Crocetin did not affect the cell growth at concentrations up to 30 mg 100 ml(-1). The major pigment has been identified as the crocetin di-neapolitanosyl ester, a new pigment not yet reported in Crocus sativus plant. The other pigments were mixed forms of neapolitanosyl, gentiobiosyl, and glucosyl esters. Glucosyltransferase activity was measured during the culture cycle and indicated that the bioconversion capacity was higher at the end of the exponential phase. The formation of glycosyl esters was highest during the first 24 h of incubation and the maximal concentration of products was achieved after 4 days. The culture had the capacity to form up to 9 mg g(-1) dry wt, glycosyl esters with 30 mg substrate per 100 mi culture. Glucose and 24-dichlorophenoxyacetic acid added to a 12-day-old culture enhanced the glucosyltransferase activity but did not affect the yield. The formation of glycosyl esters was higher when the substrate was added by steps each day rather than supplied all at once at the beginning of the incubation period, indicating the occurrence of impediment to crocetin uptake.