Three patterns of mutual intimate partner violence (IPV) are proposed, based on frequency and severity: Male primary perpetrator (MPP), female primary perpetrator (FPP), and symmetrical (SYM). Patterns and effects of ethnicity were examined with 445 African American, Euro-American, and Mexican American low-income women experiencing mutual IPV. More relationships were classified as MPP (54%) than SYM (35%) or FPP (11%). Comparing women's and men's perpetration of several types of IPV (e.g., threats, severe physical) indicated MPP-pattern women experienced all IPV types more often and were more likely to sustain injury than their male partners. Fewer gender differences were found in the FPP pattern. Racial/ethnic groups were more similar than different; previously reported differences may be explained by variation in socioeconomic status.