We studied the long-term effect of partial gastrectomy on bone metabolism in a well defined population of gastrectomized patients compared to an age- and sex-matched group with unoperated peptic ulcers (controls). We selected 61 individuals between 61 and 70 years old at the time of investigation who had been operated on at the same surgical department an average of 20 years earlier. Compared to unoperated ulcer patients, we found reduced bone mass of the distal forearm in the operated groups. The serum level of calcidiol was significantly reduced in Billroth I (BI) operated women and insignificantly lower in the other operated groups, In men, ionized and total calcium was reduced, and 24-hour excretion of hydroxyproline in the urine was increased (p < 0.05). Biochemical signs of osteomalacia mere found in one gastrectomized patient only, There were no significant differences between operated and unoperated patients in serum levels of alkaline phosphatases, iPTH, calcitriol, or the 24-hour urine calcium/creatinine excretion, even though there was a trend towards lower 24-hour urine catcium/creatinine ratio and increased levels of iPTH in the operated groups. There was no correlation between the daily alcohol consumption or cumulative tobacco consumption and bone mineral content in each group. Gastrectomized women smoked much more than control women, and smoking may be a determinant factor for the bone loss, as it is in healthy persons. Operated patients had a lower intake of milk products, All patients were exposed to sunlight for more than 3 hours/week. It is suggested that osteopenia after gastrectomy might be caused by calcium depletion rather than lack of vitamin D. The consumption of tobacco but not of alcohol was connected to bone loss.