Chloroform and ethanol extracts of root bark of Securidaca longepedunculata, Wrightia natalensis and Rhoicissus tridentata were investigated for their in vitro activity on the contraction of corpus cavernosal smooth muscle of white New Zealand rabbits. Some of the extracts of these plants relaxed the corpus cavernosal smooth muscle at low concentrations. The highest activity was obtained from Securidaca longepedunculata chloroform extracts at a concentration of 13.0 mg/ml, which induced 66.6% relaxation. Viagra was used as a positive control in this study. Extracts of Securidaca longepedunculata added to human spermatozoa affected certain sperm parameters negatively at 6.5 mg/ml and higher whilst there was no effect at 1.0 mg/ml.