6 children with protein calorie nalnutrition (PCM) and 5 control children received a single dose of sulfadiazine (25 mg/kg body weight). Absorption rate constant in the control group was 0.735 ± 0.058 h^–1 and in PCM 0.519 ± 0.03 h^–1. Peak blood levels of the drug were similar in both groups. However, the time to reach the peak was shorter in the control than in the PCM group. Elimination rate constant and half life of the drug were 0.0233 ± 0.0026 h-¹ and 31.78 ± 3.82 h, respectively, in the PCM group and 0.0332 ± 0.0022 h^-1 and 21.27 ± 1.51 h, respectively, in the control group. These values differ significantly from each other. The area under the blood concentration-time curve was more than double in the PCM group as compared to the control group. Urinary excretion of the drug in 48 h was significantly more in control (19.3 ± 1.4 mg/kg body weight) in comparison to the PCM group (13.6 ± 1.7 mg/kg body weight). However, the free drug concentration in urine/kg body weight was not altered in the PCM group. There was a significant decrease in quantity of acetylated drug in the PCM group as compared to the controls. In view of these observations, therapy with sulfadiazine in children suffering from PCM requires reconsideration.