Suspension cultures of Catharanthus roseus (C. roseus) were elicited with fungal cell wall fragments of Aspergillus niger (A. niger), Fusarium moniliforme (F. moniliforme), and Trichoderma viride (T. viride). The effects, of elicitor dosage, exposures time, and age of subculture on ajmalicine accumulation were studied. A higher concentration of elicitor extract responded positively to C. roseus suspension cultures. Ajmalicine accumulation increased by about 3-fold when cells were treated with A. niger, F. moniliforme, and T. viride. The maximum ajmalicine production (75 mug g(-1) dry weight (DW)) was observed in cells treated with T. viride. Cell cultures were elicited with 5% preparation of A. niger, F. moniliforme, and T. viride and exposed for 24, 48,,72, and 96 h. for elicitation. Suspension cultures elicited with T viride for 48 h showed a 3-fold increase (87 mu g(-1) DW) in ajmalicine contents, whereas A. niger and F. moniliforme synthesized a 2-fold increase in alkaloid and yielded 52 and 56 mug g(-1) DW ajmalicine, respectively. C. roseus cells of different age (5,10, 15, 2:0, and 25 days old) were treated with a 5% elicitor of A. niger, F. moniliforme, and T. viride and investigated elicitors activity at different age of cell cultures. Maximum yield 166 mug g(-1) DW of ajmalicine was synthesized in 20 day old suspension cultures treated with T. viride. A longer period of incubation of cell cultures with elicitors adversely affected the ajmalicine synthesis.