The hypothesis that ethylene regulates prostrate stem growth was investigated using stolons of strawberry clover (Trifolium fragiferum L. var. Salina). Stolons became erect when treated with ethylene or 2-chloroethylphosphonic acid. Curvature was visibly detectable 2 hours after ethylene treatment, and subsequent stem elongation was rapid. Indoleacetic acid application to prostrate stolons caused only a small transitory curvature persisting less than 48 hours. Indoleacetic acid-stimulated curvature was accompanied by an increase in ethylene evolution. When stolon curvature was induced by placing strawberry clover plants in darkness or by applying gibberellic acid, ethylene production did not parallel stolon curvature.