Abstract: In the present research, effect of caffeine on structure and ultrastructure of shoot apical meristem of Phaseolus vulgaris L. was investigated. The present study showed that low concentrations of caffeine (<22.5 ppm) had no pronounced effect on the growth of bean seedlings and structure of shoot apical meristem, but higher concentrations of caffeine (40-60 ppm) had severe inhibitory effects. Electron microscopy (TEM and SEM) studies showed that apical meristem size and number of leaf primordia was decreased under caffeine treatment. Also in some meristem cells, formation of cell wall was incomplete. Present findings show that a lack of division in strategically located cells in primordia and during organogenesis could produce the organ abnormalities described. The observation that cytokinesis defects can be observed in developing primordial and meristems supports this.