['To investigate the impact of cigarette smoking on sperm nucleoprotein transition and its association with sperm motility in infertile males.', 'We examined the semen quality and sperm nucleoprotein transition of 116 non-smokers and 113 heavy smokers (aged 25 -50 years) who visited the Research Institute of Obstetrics and Gynecology for male infertility. We determined the rate of individual sperm nucleoprotein transition by aniline blue staining and analyzed the correlation of cigarette smoking with routine semen parameters and the rate of sperm nucleoprotein transition. Based on the smoking index (SI) derived from smoking frequency (no. of cigarettes/d) multiplied by smoking duration (yr), the men with SI = 0 were considered as non-smokers, and those with SI > or = 200 as heavy smokers.', 'The rate of abnormal sperm nucleoprotein transition was significantly higher in the asthenozoospermic (23.5 +/- 9.4, P < 0.01) and oligoasthenozoospermic (28.2 +/- 9.2, P < 0.01) than in the normozoospermic males (19.0 +/- 9.0). Compared with the non-smokers, cigarette smoking remarkably reduced sperm nucleoprotein transition in both the men with normal sperm motility (21.9 +/- 9.8 vs 16.8 +/- 7.7, P < 0.01) and those with abnormal sperm motility (26.0 +/- 9.9 vs 22.7 +/- 8.8, P < 0.05). A weak correlation was observed between the rate of sperm nucleoprotein transition and routine semen parameters.'] Does [ Cigarette smoking decrease sperm nucleoprotein transition in infertile males ]?