Nineteen patients suffering from chronic respiratory disease were evaluated before, during and after ethamivan administration by serial measurement of arterial pH, pCO(2), plasma ethamivan levels and alveolar ventilation. Ethamivan was administered intravenously as a single injection of 50 mg. in five patients; as an injection of 25 mg./kg. in five patients; as an intravenous injection of (a) 50 mg. over 15 minutes and (b) 150 mg. over 15 minutes in five patients; and finally as an oral dose of 300 to 500 mg. in five patients.Plasma levels of ethamivan became unmeasurable within 15 minutes of receiving the largest dose. Alveolar ventilation increased only in patients receiving the highest intravenous dose, and no significant changes in blood gases were elicited in any patient.