The intravenous administration of narcotics and other drugs may frequently result in serious and often life-threatening pulmonary, cardiac, and vascular complications. Drug contaminants and nonsterile injection techniques with resultant infection are responsible for many of these complications. Selected cases from 28 patients with these complications are illustrated. Common pulmonary complications recognized roentgenographically include pulmonary edema following heroin overdose, pulmonary infections, and septic pulmonary emboli. A manifestation of chronic intravenous drug use, angiothrombotic pulmonary hypertension, has only recently been recognized clinically, but has a distinctive roentgenographic appearance that may enable its more frequent detection in the future. The cardiac complications of endocarditis are particularly well-suited for radiographic detection, especially when valvular damage occurs. Septic pulmonary emboli, easily detected roentgenographically, may be the only clue to the diagnosis of right-sided endocarditis. The vascular complications include mycotic aneurysm, and arterial occlusion, both easily diagnosed by angiographic studies. Radiologists familiar with these complications may aid other clinicians in recognizing these diseases.