When couples elect to defer child bearing, the effects of age on reproductive potential must be considered. The impact of advancing age on female reproductive potential has been well documented. Relatively less attention, however, has been directed toward the effect of age on male reproductive function. Although less pronounced than its effect on female fertility, advancing age does have an impact on male reproduction. Among men, increasing age is associated with a decrease in sexual function as well as changes in testicular histology and a decline in basic fertility parameters. Additionally, there is an identifiable association between advanced paternal age and subsequent birth defects. These issues should be borne in mind when men are counseled regarding the age at which they elect to establish families.