In this study we investigated whether leptin and TNFα levels change with improvement in body weight with antituberculotic therapy in active tuberculosis patients. 30 patients (8 females and 22 males) with active pulmonary tuberculosis formed the patient group, and 25 sex- and age-matched healthy subjects (8 females and 17 males) served as the control group. Body weight, body mass index (BMI) and serum leptin and plasma TNFα levels are measured before and in the sixth month of therapy in all patients. Before the initiation of therapy, BMI of the patients was significantly lower than BMI of the controls (20.2 ± 1.6 vs. 25.2 ± 2.7 kg/m2, respectively; p < 0.05). After treatment, BMI of the patients increased significantly to 21.4 ± 1.9 kg/m2 (p < 0.05), but was still lower than that of the controls (p < 0.05). Pretreatment serum leptin (4.5 ± 0.9 vs. 2.1 ± 0.2 ng/ml, respectively; p < 0.05) and plasma TNFα (27.9 ± 3.4 vs. 23.9 ± 3.0 pg/ml, respectively; p < 0.05) levels of the patients were significantly higher than those of the controls. After treatment, serum leptin levels increased to 6.7 ± 2.2 ng/ml, but this rise was not statistically significant (p > 0.05). Treatment did not result in any significant change in TNFα levels, either. Δ leptin was highly related to Δ BMI in patients with tuberculosis (r = 0.68, p = 0.02). In the pretreatment period, there was a significant correlation between leptin and TNFα levels in the whole patient group (r = 0.78, p < 0.001), and in female (r = 0.74, p < 0.001) and male patients separately (r = 0.74, p = 0.035). In conclusion, leptin and TNFα may be responsible for the weight loss in pulmonary tuberculosis patients, but their levels do not change with improvement in body weight with antituberculotic treatment. Copyright (C) 2000 S. Karger AG, Basel.