Oseltamivir was administered at 1.0 mg/kg b.i.d. to 13 neonates exposed to influenza H1N1. No influenza, neurologic, or laboratory adverse effects occurred. The mean Cmax values for oseltamivir and oseltamivir carboxylate were found to be lower than those reported for children 1 to 5 years old, whereas Tmax values were similar to children 1 to 5 years old. Age and gender were found to significantly affect oseltamivir clearance.