The CPR is the primary federal entity for supporting a range of population studies that aim to: understand reproductive health and biology of the male and female; establish new diagnostic and treatment methods for infertility; develop contraceptive methods that are safe, effective, inexpensive, preferably reversible, and acceptable and those that reduce the spread of sexually transmitted diseases; evaluate contraceptive methods, drugs, devices, and surgical procedures related to reproductive health; ascertain the determinants of fertility and mortality; understand the consequences of population size and distribution changes; define the antecedents and consequences of conditions that precipitate migration and immigration; examine resources and other contextual influences on family functioning and child well-being.