SIGMA, JURNAL SAINS DAN TEKNOLOGI, Vol. 13, No. 1 Januari 2010, ABSTRAK : An experiment to study effect of elicitor derived from sacchoromyces cerevisiae (Hansen) on ajmalicine content of catharanthus roseus (L) G. Don. calus cultures has been conducted. Callus was induced from leaf segment and grew on medium zenk (1977) supplemented with 2,5 x 10-6 M NAA dan 10-5 M BAP. Calus on the third subcultur level was elicited with elicitor derived from S. cerevisiae. The following concentration of elicitor tested were 0 ; 0,5 ; 1,0 ; ang 2,5 % (g/v), qualitatively and quantitatively by using high performance liquid chromatography (HPLC).Ajmalicine content was influenced by concrentration of elicitor and harvesing time. A significant increase of ajmalicine content (303,475 kurang lebih 5,602 mg/gDW) was achieved by addition of elicitor of 0,5 % (g/v) after 36 hour. This study show a significant increase of ajmalicine content in C. roseus callus cultures after being challenged with S. cerevisiae elicitor i.e 69,334 %