Abstract: Objective To understand the status of the forearm bo ne mineral density(BMD)in mid-aged and elderly people.To find the potential factors influencing BMD.Methods 1214 mid-aged and elderly people were examined,in Tianlin,Fenglin and Xietu sub districts in Xuhui District,Shang hai.BMD were measured at four regions in left forearm,containing distalr adius and ulna 1/3 total,distal radius where the distance of radius and ulna was 8mm,ultra-distal radius,by single energy X-ray densitometer.Results The BM Dat all of the four regions descended with the age increasing,and more quickly in female than in male.The average BMD was higher in male than in female,in the same age and region.And distal radius 1/3 total had the highest BMD of the four regions.The incidence of low bone mineral density and osteoporosis in distal forearm 1/3 radio-total ascended with the age increase,with an exception that males aged 60~65 had higher incidence than those aged 55~60.Multiplied logistic regression shows that males had a lower risk to be low bone mineral density,the odds ratio was 0.19 compared with female.With the group aging from 50 to 55,the odds ratio in the group aging from 55 to 60,60 to 65,65 to 70 were 3.17,5.13,15.03.Compared with those earning a monthly salary less than 1 000,the odds ratio was 0.70 in the those earning a salary more than 1 000.Those taking calcium tablet share an odds ratio of 1.36,compar ing with those who don't.Conclusion The incidence of low bone mineral density is high in mid-aged and elderly population,and it is related with sex,age,monthly income,calcium tablet intake.