Addiction is a major problem confronting the whole world today. Disruption of interpersonal relationships, economic loss, and crimes against property are frequent consequences. Harm to the individual himself extends to all physiological systems. In the present study, we examined semen samples of six addicts by light and electron microscopy. Oligoasthenospermia was demonstrated in five patients, and necrospermia was observed in one patient. Severe degenerative changes of the sperm heads were noted. Granular condensation of the chromatin with nuclear vacuoles was demonstrated. Persistent cytoplasmic droplets were frequently observed. Degenerated tails showing fragmentation of the plasma membranes and numerical aberrations of the 9 + 2 configuration were also present, together with thickened and disorganized fibrous sheaths. These results confirm the deleterious effects of addiction on the entire sperm structure.