Cooper and associates (1973) developed a method of ascertaining the lithium dosage required to attain a therapeutic serum level of 0.6 to 1.2 mEq/L. However, reports about the safety and accuracy of their method in children are limited (Geller & Fetner 1989). This study relates our experience with using this method in children. Subjects were 16 conduct-disordered children (13 males, 3 females), ages 8.97 to 17.14 years (mean, 12.73 +/- 2.12), who were treated with lithium to decrease aggressive behavior. Following a lithium 600-mg loading dose, a 24-hour serum lithium level was drawn from which a "predicted" lithium dosage was established. These dosages ranged from 600 to 1,800 mg/day (mean, 1,312.5 +/- 450) and the corresponding serum lithium levels at steady-state ranged from 0.58 to 1.13 mEq/L (mean, 0.87 +/- 0.15). No severe side effects were encountered. This suggests that the method is safe and useful for predicting lithium dosages in children.