There have been several reports indicating that the quality and quantity of human spermatozoa are facing a serious decline. This leads some scientists and environmentalists to believe that the human species is approaching a fertility crisis. Several factors have been claimed to be the attributable causes of the decline in male fertility potentials. These include heavy metals and various chemical agents widely used in agriculture and industry. Moreover, other physical factors such as the increased global temperature and radiation exposure as well as the biologic factors such as the contamination of phyto- and xeno-estrogen in the environment could detrimentally affect male reproductive function. These effects can result in, not only a reduction in sperm concentration, but also alterations in sexual behavior, mood disorders and the presence of genital cancers. The knowledge in male gonadal toxicity, therefore, is very useful in understanding the impact of environment to the male reproductive system. This will lead us to protective strategies to avoid the adverse effects of environmental factors on the male fertility.