Study Design: Cross-sectional study comparing isometric lumbar extensor strength (ILES) in individuals who smoke and nonsmokers with and without low back pain (LBP). Objectives: To examine the differences in ILES between individuals who smoke and nonsmokers with and without LBP. Background: Given the evidence for general muscle weakness in individuals who smoke and in individuals with LBP, we were interested in examining the interrelationships between back strength, in particular ILES, and LBP in individuals who smoke and nonsmokers. Methods and Measures:The study involved 76 men (age range, 30-50 years) in 4 groups, namely, nonsmokers with LBP (NS-LBP), a control group of nonsmokers without LBP (NS-C), smokers with LBP (S-LBP), and a control group of smokers without LBP (S-C). ILES was measured at 7 angles of lumbar flexion, specifically 72°, 60°, 48°, 36°, 24°, 12°, and 0°. ANOVA and Scheffe post hoc comparison tests were used to analyze the data. Results: Nonsmokers with LBP had less muscle strength than those without LBP (PϽ.01). However, the strength of smokers with and without LBP was comparable (P Ͼ.05). Both groups of individuals who did not smoke were stronger than the 2 groups comprised of smokers. Conclusions: Individuals who smoke were weaker than those who did not smoke, but no difference in strength was noted between smokers with and without LBP. Although smoking appears to be an important cofactor in the etiology of LBP, the degree to which smoking is a primary, secondary, or a component of a combined etiology warrants further study.