Design: Cohort study.

Setting: Military recruiting station, Teplice, Czech Republic.

Patient(s): Ten current smokers (20 cigarettes per day for at least 2 years, exposure confirmed by urine cotinine) who also consumed alcohol and 15 nonsmokers. All patients were exactly 18 years old, healthy, and of unproven fertility.

Main Outcome Measure(s): Sperm aneuploidy by multicolor fluorescence in situ hybridization for chromosomes 8, X, and Y; conventional semen analyses; computer-aided sperm analysis for motility; and sperm chromatin structure analysis.

Results: Smokers showed elevated frequencies of sperm aneuploidy (Y disomy, P <0.001; aggregate of X, Y, and 8 disomies, P <0.01); reduced linearity of sperm motion (P <0.05); and more "round-headed" sperm (P <0.01). Smokers' semen contained fewer sperm (P <0.001) and fewer motile sperm (P <0.02), which was attributable, in part, to shorter abstinence intervals among smokers (P <0.02).

Conclusion(s): Cigarette smoking among teenagers was associated with increases in disomic sperm and a diminution in Specific aspects of semen quality. Such defects may affect male fertility and may increase future chances of fathering Offspring with aneuploidy syndromes. (Fertil Steril(R) 1998;70:715-23. (C) 1998 by American Society for Reproductive Medicine.).