Reproduction is a complex, stepwise series of processes that begins with gametogenesis, continues through gamete interaction, implantation, embryonic development, growth, parturition, and postnatal adaptation, and is completed with the development and sexual maturation of the newly formed organism. These reproductive processes do not take place in a chemically pristine environment, but rather in an environment increasingly contaminated with the products and by-products of the chemical age in which we live. Some environmental pollutants are known to be carcinogenic, mutagenic, or toxic to the reproductive system, but most have not been adequately tested for reproductive toxicity. Just as reproduction is complex, biological mechanisms underlying toxicology are similarly complex and involve absorption, distribution, metabolism (toxification and/or detoxification), excretion, and repair. The synthesis of these sciences into the relatively nascent science of reproductive toxicology includes teratology, pharmacology, epidemiology, and occupational and environmental health. Female reproductive function (especially pregnancy outcome) has historically been the focus of attention, but there is increasing interest in the effects of chemical exposure on male reproductive function. Several reports have documented the physiology, biochemistry, and toxicology of male mammalian reproduction, and evaluated susceptibility of the male to the effects of exogenous chemicals.