The effect of ciprofloxacin treatment on semen analysis was studied. Six apparently healthy volunteers with age ranging from 30-51 years were included in this study. Ciprofloxacin tablet (500 mg) was given to each volunteer twice daily for 14 days. Semen analysis was performed for them before ciprofloxacin treatment and 2,4 and 6 weeks after treatment. Four weeks after treatment, there was a statistically significant reduction in total sperm count by 53.4% (from 157.16 ± 23.7 to 73.17 ± 19 millions, p < 0.001), in percentage of actively motile sperms by 40.5% (from 35±7.06 to 20.83± 5.23, p<0.001) and in percentage of viable sperms by 15.2% (from 67.6 ± 6.01 to 57.33± 9.48, p < 0.025). It is concluded that administration of ciprofloxacin (500 mg x 2 for 2 weeks) had, therefore, resulted in a significant reduction of various parameters of semen analysis. A finding, if proved to be true, should be taken in consideration during ciprofloxacin treatment for any type of infection in males.