Although osteoporosis is a common clinical disorder associated with gastric surgery, long-term effects of gastrectomy on bone metabolism are still unclear. The purpose of this study was to clarify the incidence and risk factors of osteoporosis after gastrectomy using univariate and multivariate analyses of quantitative measurements. The study included 59 patients who had undergone gastrectomy more than 5 years before. There were 38 men and 21 women, aged 37-81 years, mean 64 years. Bone mineral density (BMD) of L2-L4 spine was measured using dual-energy X-ray absorptiometry (DXA). Absolute value of BMD (g/cm2) and age- and sex-matched BMD (%) were given. The mean BMD was 0.766 g/cm2, and the incidence of osteoporosis (BMD less than 0.70 g/cm2) was 37%: 18% in men and 71% in women. The mean age- and sex-matched BMD was 85.9%: 87.5% in men and 83.1% in women. Univariate and multivariate analyses revealed that BMD was significantly associated with the age and sex of patients, but was not influenced by the type of gastrectomy (partial versus total) and years after operation (< 20 versus 20 <). Our study clarified the fact that postgastrectomy osteoporosis was frequent in the aged or female patients. BMD should be evaluated after gastrectomy, especially in the aged and in women.