Updating a 1977 review, this review of the research concerning parents' effects on their children's development asks what progress has been made in understanding such effects during the last decade. After presenting findings of the earlier review, discussion focuses on five areas of research: temperament, attachment, cognitive development, language acquisition, and socialization. It is concluded that increased knowledge of parents' effects on children's development has revealed how much remains unknown. Progress has been made over the past decade, but the progress has been in problem finding rather than in problem solving, divergent rather than convergent. Researchers should focus on the limits of parents' effects on their children's development and conduct systematic experiments. Parent training programs can be both the medium and the message in this area of research. A 26-page reference list is appended. (RH)