We determined whether habitual cigarette smoking alters insulin-stimulated glucose transport and GLUT4 protein expression in skeletal muscle. Vastus lateralis muscle was obtained from 10 habitual cigarette smokers and 10 control subjects using an open muscle biopsy procedure. Basal 3-O-methylglucose transport was twofold higher (P < 0.01) in muscle from habitual smokers (0.05 +/- 0.08 vs. 1.04 +/- 0.19 mumol ml-1 h-1; controls vs. smokers respectively). Insulin (600 pmol l-1) increased glucose transport 2.6-fold (P > 0.05) in muscle from control subjects, whereas no significant increase was noted in habitual smokers. Skeletal muscle GLUT4 protein expression was similar between the groups. FFA levels were elevated in the smokers (264 +/- 49 vs. 748 +/- 138 mumol l-1 for control subjects vs. smokers; P < 0.05), and serum triglyceride levels were increased in the smokers (0.9 +/- 0.2 vs. 2.3 +/- 0.6 mmol l-1 for control subjects vs. smokers; P < 0.05). Skeletal muscle carnitine palmitil (acyl) transferase activity was similar between the groups, indicating that FFA transport into the mitochondria was unaltered by cigarette smoking. In conclusion, cigarette smoking appears to have a profound effect on glucose transport in skeletal muscle. Basal glucose transport is markedly elevated, whereas insulin-stimulated glucose transport is impaired. These changes cannot be explained by altered protein expression of GLUT4, but may be related to increased serum FFA and triglyceride levels. These findings highlight the importance of identifying habitual cigarette smokers in studies aimed at assessing factors that lead to alterations in lipid and glucose homeostasis in people with non-insulin-dependent diabetes mellitus (NIDDM).