AIM: To obtain epidemiological information on physical assault in a high risk group of New Zealanders. METHOD: Rates of physical assault in the preceding twelve months were ascertained by interview in a cohort of 21 year old, Dunedin-born men (n = 482) and women (n = 462). RESULTS: Forty-five percent of the men and one quarter of the women reported at least one physical assault, either completed, attempted or threatened. A small proportion of these received medical treatment. Most serious assaults were by a perpetrator who was thought to have been drinking alcohol. Most assaults on men were by strangers but partners carried out more assaults against women, especially those receiving medical treatment. One quarter of all assaults on women were by other women, compared to 15% of the assaults on men. Differences between patterns of assaults on women and on men are discussed. CONCLUSION: It is important for doctors to be aware of the widespread occurrence of interpersonal violence in New Zealand and its underreporting.