Summary Oral feeding of male rats with plumieride (15 mg/rat/day) for the period of 60 days did not cause any significant change in the body weight of treated rats. However, the weights of testes, epididymides, seminal vesicle and ventral prostate were significantly reduced when compared to control values. The production of step-19 spermatids was reduced by 87.26% in plumieride treated rats. The population of preleptotene and pachytene spermatocytes were decreased by 64.26% and 55.13% respectively. Spermatogonia and sertoli cell population was also affected. Plumieride treatment resulted in an arrest of spermatogenesis without any systemic side effect. Sperm motility as well as sperm density was reduced significantly. The number of mature Leydig cells was decreased and complete suppression of fertility was observed. A significant fall in the protein and sialic acid contents of the testes, epididymides, seminal vesicle and ventral prostate as well as glycogen content of testes was also noticed. Fructose in seminal vesicle was lowered whereas testicular cholesterol was elevated. There was no significant change in RBC and WBC count, haemoglobin, haematocrit and sugar in the whole blood and total protein, cholesterol, phospholipid and triglycerides in the serum. Conclusion: Plumieride administration arrests spermatogenesis in male rats without noticeable side effects. For the clinical use more experiments should be carried out in a phased programme.