PURPOSE: The purpose of the study was to assess the effect of cigarette smoking on indicators of bone strength across a wide age range, controlling for physical activity and neuromuscular performance. METHODS: We conducted a cross-sectional study with 41 smokers (mean age +/- SD, 41.0 +/- 16.1 yr) and 53 nonsmokers (47.5 +/- 18.2 yr) of both sexes. Bone strength indicators (BSI) were assessed in the lower leg and forearm by peripheral quantitative computed tomography along with physical activity, muscle cross-sectional area, and maximal voluntary muscle force. RESULTS: Physical activity level and muscle cross-sectional area of the leg and arm were similar in smokers and nonsmokers. Although trabecular volumetric bone mineral density and epiphyseal bone mineral content, both indicators of BSI, decreased with age in the nonsmokers' tibia (P