The effect of different plant growth regulators (PGR) and elicitor treatments on the alkaloid profile variation of Catharanthus roseus was investigated in the present study. The PGR used were paclobutrazol (PBZ), gibberellic acid (GA(3)) and Pseudomonas fluorescens elicitors (PF Elicitors). The estimated alkaloids were ajmalicine, catharanthine, tabersonine, serpentine and vindoline. In roots, the ajmalicine content increased significantly under all the treatments on all sampling days. In roots, the catharanthine contents increased with the age in control and growth regulator treatments, but the increase was not prominent and significant in PGR treatments when compared to controls. The serpentine contents of the plant increased with PGR treatments, but the increase was more prominent in PBZ treatments when compared to other treatments. The increase was in the order PBZ > PF Elicitors > GA(3). C. roseus never showed any significant increase in tabersonine contents in the roots under GA(3) treatments, but it increased significantly under PBZ and PF Elicitors when compared to control plants. The root vindoline contents increased with PBZ and PF Elicitors treatments but the decreased under GA(3) treatments when compared to control plants. Our results have good significance, as these increases the secondary metabolites of this traditional medicinal plant. (C) 2008 Elsevier Ltd. All rights reserved.