With the exception of intra-family murder and child abuse, there has been very little research on violence between family members. However, preliminary results of this study indicate that even at age 17 and 18, 62 percent of siblings had hit each other during the previous 12-month period. Also, physical fights between husband and wife have occurred in over half of all marriages. The authors summarize theories of family violence and propose specific areas of further research. The theories of violence fall into three categories: (1) intra-individual theories; (2) social-psychological theories; and (3) socio-cultural theories. The proposals for research are followed by a discussion of research methodology. (RWP)