Summary25 young asymptomatic heroin addicts were investigated. Pulmonary perfusion scintigraphy was altered in 94. The functional testing of pulmonary function performed in 9 of them revealed a diminished diffusion capacity in 2. Liver function tests were slightly altered in 40 %. Hepatic scintigraphy showed functional heterogeneity in 87 % with a splenic hyperactivity in 47 %. AgHBs was positive in 1 out of 24 cases tested. These data are compared with those reported in the U.S.A. and their pathophysiology is discussed.