Diosgenin is a steroidal sapogenin present in fenugreek and Dioscorea spp. as glycosides (saponins). Diosgenin has already been reported to inhibit osteoclastogenesis and to stimulate osteogenic activity of osteoblastic cells in vitro, and to exert some antiosteoporotic effects in rats in vivo. The aim of the present study was to investigate the effects of diosgenin administration on the skeletal system of rats with normal estrogen level and with estrogen deficiency induced by bilateral ovariectomy. The experiments were carried out on 3-month-old non-ovariectomized and ovariectomized Wistar rats, divided into control rats and rats receiving diosgenin (50 mg/kg p.o. daily) for 4 weeks. Serum bone turnover markers, bone mass and mineralization, histomorphometric parameters and mechanical properties were studied. Diosgenin improved some investigated parameters in both non-ovariectomized and ovariectomized rats, in which estrogen deficiency induced osteoporotic changes. Diosgenin increased compact bone formation and probably inhibited cancellous bone resorption, which led to improvement of mechanical properties of compact and cancellous bone. In conclusion, this in vivo study demonstrated that diosgenin may be one of sparse compounds increasing bone formation.