Pyrazinamide plasma concentrations were determined in 34 children (median age, 3.32 years) 1 month after commencing antituberculosis treatment. The median (interquartile range) peak concentration was 30.7 (25.5, 35.0) mg/L after a median dose of 23 mg/kg. Peak concentrations < 20 mg/L were found in 5 children (15%) and such low concentrations were particularly likely after doses < 20 mg/kg.