The serum rifampin level after smoking was estimated by various times in 10 smoking healthy and 30 smoking tuberculosis inpatients compared with 10 non-smoking healthy and 29 non-smoking tuberculosis inpatients, with equal dose of 600 mg rifampin. The concentration of the rifampin was calculated by range matrix analysis area under the curve (Auc.) The Auc0-8 of the healthy and smokers were 75.75 and 110.38 mg.h/L respectively, while in the tuberculosis group, the Auc0-8 of smokers and non-smokers were 30.17 and 43.26 mg h/L respectively. The above figures as compared with the smoking and non-smoking group was decreased by varying degrees in Auc. The difference is significant statistically (P value less than 0.05).