AIM:To study the effects of GYB (Ext.of Fructus cnidii and Semen cuscutae)on osteoporosis rats induced by retinoic acid.METHOD:The osteoporosis of rats was induced by administering 70 mg/kg retinoic acid for 15 days.Having been fed with GYB,at the dose of 100,200,400 mg/kg·d,extracts of Fructus cnidii and Semen cuscutae,at the dose of 200 mg/kg·d,to the rats continuously for 5 weeks,the concentrations of serum calcium(s-Ca),serum phosphorus(s-P),tartrate resistant acid phosphatase in serum(s-TRAP)and alkaline phosphatease in bone(b-ALP)were measured by colorimetric method.The concentration of osteocalcin in serum(s-BGP)was measured by competitive radio immunological assay.The content of bone calcium(b-Ca),and bone phosphorus(b-P)in femur were determined by colorimetric method.Bone mineral density(BMD)of femur and lumbar was determined by Dual Energy X-ray Absorbtiometry(DEXA).Biomechanical characters of femur were measured by three point bending test.Histomorphometry of bone trabecula was analysed by scanning electron microscope.RESULT:The BMD of femur and the content of b-Ca,b-P were increased.The levels of s-TRAP and s-BGP were decreased.The resistance of bending and compression of femur was enhanced.The form of bone trabecula was bettered,MTT and trabecula square percentage(TS%)were increased obviously too.CONCLUSION:Fructus cnidii,Semen cuscutae and GYB have antiosteoporotic effects in rats induced by retinoic acid.