Viewing illegitimacy from an individualist, deviant behavior frame of reference has not been useful because of the high prevalence of illegitimacy. Theories attributing illegitimacy to the social marginality of subcultures are inadequate to explain illegitimacy among working class and middle class children. Theories based on the notion that mothers of illegitimate infants are mature women do not explain illegitimacy among teenagers. Analysis of current research indicates that pregnancy is occurring among teenagers because sociocultural factors pressure them into making decisions that require a more mature level of moral judgment than they possess. Preventive measures regarding illegitimacy should be based on theories of normal psychosocial adolescent development that include socialization experiences for persons at a given level of cognitive and moral development in the context of a heterogeneous society. (Author/HLM)