PURPOSE: To obtain data on the relationships between weight for height status, in adolescents and their parents, and adolescents' perceptions of body image and weight-loss behavior. METHODS: Weight and height were measured in both parents and adolescents from 213 families with an adolescent child aged 14-15 years who were participating in a community-based study of risk factors for coronary heart disease in Geelong, Australia. Information on adolescents' perceptions of body image, desired weight, and weight loss behaviors was obtained by questionnaire. RESULTS: Forty-one percent of the girls and 14% of the boys considered themselves overweight while 18% of both boys and girls were in this category on the basis of their body mass index (BMI). Most boys tended to see themselves as of normal weight while only girls below the 10th centile for BMI consistently rated themselves as normal. Adolescents who rated themselves as slim had parents whose BMI was significantly lower than that of the parents of adolescents who rated themselves as overweight. A significant proportion of adolescent girls (69%) and boys (27%) had at some time tried to lose weight. Female, but not male, adolescents of normal BMI who had tried to lose weight were themselves heavier and had significantly heavier mothers, but not fathers, than those in the normal range for BMI who had not attempted to do so. Adolescents who perceived an advantage in gaining weight had significantly shorter and lighter, but not leaner, fathers than those who perceived an advantage in losing weight. Only individuals below the 10th centile for BMI appeared to be content with their weight. On average the weight desired by girls and boys in the normal range for BMI was 6.6 and 2.0 kg less than their actual weight, while their desired height was 8.0 and 12.8 cm more than their actual height. CONCLUSIONS: The findings confirm gender differences in perceptions of and attitudes to body weight and body build. They also provide evidence for an association between adolescents perceptions of body weight and parents' weight for height status and suggest that the size of the "gap" between desired and actual weight is associated with the prevalence of weight-loss behavior.