The contribution of the lungs to the clearance of exogenous dopamine was analyzed in humans by measuring plasma pulmonary concentrations of dopamine and the pulmonary plasma flow before and after infusion of dopamine. Contribution of the lungs was defined as the ratio between clearance by the lungs and the total plasma clearance of dopamine. Significant transpulmonary gradient of plasma dopamine was observed with infusions at rates of 1.0 and 2.0 micrograms.kg-1.min-1, but not at 0.5 micrograms.kg-1.min-1. The calculated contribution values were 4.90%, 19.23%, and 20.60% at the doses of 0.5, 1.0, and 2.0 micrograms.kg-1.min-1, respectively. The results suggest that the clearance mechanism of the lungs is effective when the plasma dopamine level becomes sufficiently high, and that the lungs clear 19%-21% of clinical doses of dopamine.