The pharmacokinetic characteristics of a new antidepressant, viloxazine hydrochloride, were investigated in five males and five females to study sex differences. Plasma levels were determined over a period of 9 h after a single dose of viloxazine of 100 mg (expressed as base). The half life of the drug was in the range of 2.19 - 4.21 for females and 2.61 - 4.31 h for males. The maximum plasma levels occurred in 29 - 171 min of the oral dose for females and 54 - 155 min for males. They reached 1382 - 1769 ng/ml-l for females and 1108 - 2932 ng/ml for males. Pharmacokinetic data were not statistically different between males and females.