The effects of exogenous estrone, estradiol-17β and gibberellic acid (GA3) on stem elongation in tall (Alaska) and dwarf (Meteor) cultivars of Pisum sativum grown under red light and under natural illumination have been studied. Test compounds were formulated in a number of ways and applied by a variety of methods. GA3 elicited a characteristic response in almost all experiments, with elongation in the dwarf cultivar being stimulated to a greater extent (relative to the control) than in the tall cultivar, but no effects of steroidal estrogens were observed on any occasion. Nor was there evidence of any interaction between exogenous GA3 and estrone. The lack of effect of estrone did not appear explicable on the basis of seedling age and the claim that red light treatment is a prerequisite for estrone action was not substantiated. Two other dwarf pea cultivars viz. Feltham First and Little Marvel also responded to GA3, but not to estrone. The disparity between the lack of estrone effect on stem elongation reported here and the positive effect reported elsewhere in the literature is discussed.