The authors present a prospective study of a rapid desipramine dose adjustment on the basis of a 24-hour plasma concentration after a single 150 mg dose. For this, they use a prediction table constructed from data in the literature showing strong correlation between steady-state plasma levels and 24-hour single-dose levels. Despite the fact that desipramine action is not always linear, the method appears to be feasible and valid. In an attempt to reach a 150 ng/ml level, the authors obtained steady-state levels ranging from 85 to 317 ng/ml, with 14 of the 19 patients in the range between 125 and 250 ng/ml. Moreover, 11 of the 19 patients received a daily dose of 250 mg or more desipramine from the third day of treatment onward; in ten of these cases, this dose had been adapted.