Objective: To determine the prevalence of health and behaviour problems in a sample of children in homeless families and of psychological problems in their parents, and to assess the use of health services by homeless families., Design: A cross-sectional, questionnaire-based prevalence survey., Setting: Supported accommodation provided by a welfare service in Melbourne between May 1994 and June 1995., Subjects: 51 children from 31 families soon after housing crises., Results: More than one-third of all children had total behaviour problems scores in the "deviant" range (i.e., requiring mental health referral). Intellectual disability/developmental delay, skin problems, vision problems, recurrent headache, and asthma or other breathing problems were more prevalent in these homeless children than in a large Australian normative population. Their mothers scored higher than a large normative sample on the mental health questionnaire, most markedly for "anxiety-insomnia", "severe depression" and total score. Cost of treatment and transport difficulties were seen as barriers to using health care services., Recommendations: Australian health-care practitioners should be aware of the health and health service access problems of children in homeless families, and work to minimise their physical, emotional, developmental and academic disadvantages. Psychological support services should be available for homeless families, particularly for mothers.