Recent advances in the modalities of quantitatively assessing bone mineral content have resulted in an increasing awareness of metabolic bone disease as a late complication following gastrectomy. In this study, 98 postgastrectomy patients were examined by quantitative computed tomography (QCT). The bone mineral density index (BMDI), defined as 100 x (measured bone mineral density divided by that of age- and sex-matched controls), was used to evaluate the actual effect of gastrectomy on bone disorders. The BMDI values following gastrectomy were 80.4 +/- 27.3, with no significant difference between men and women, or between total and distal gastrectomy. Moreover, no significant differences were observed between the BMDI values within 6 months, being 92.6 +/- 37.3, and those 6 months to 1 year post gastrectomy, being 79.6 +/- 31.2; however, a significant and sharp decrease to 70.5 +/- 36.0 was evident after 1-2 years. The regression coefficient of the BMDI measured within 2 years postoperatively was lower than that measured after 2 years. These findings suggest that the influence of gastrectomy on bone metabolism is induced within 2 years, after which the bone mineral content decreases in accordance with physiological nature. Thus, we conclude that the treatment for bone disease resulting from gastrectomy would only be effective if initiated within a short period after surgery.