A study was conducted to determine the prevalence and determinants of sun-protection practices in a sample of the non-Aboriginal population at the outdoor weekend markets in subequatorial Darwin, Northern Territory, at a time of intense sun exposure, between 11 a.m. and 1 p.m. from August to October 1992. All non-Aboriginal market-attenders who were seated within defined areas adjacent to food stalls were eligible to participate. Of 106 eligible market attenders, 105 (99 per cent) agreed to participate. Overall, fewer than 20 per cent of persons in this setting of extreme sun exposure were wearing sunscreen and less than one-third were wearing a hat. Only 44 per cent of people with a past history of skin cancer sitting in the midday sun had applied sunscreen and 61 per cent were wearing a hat; however, this was significantly more than those not reporting skin cancer (P < 0.002). The longer people had lived in the Northern Territory (compared with visitors and short-term residents) the less likely they were to have applied sunscreen in preparation for the midday sun (trend chi 2 = 3.99, P = 0.046). No association was demonstrated between the use of sunscreen and age or sex of the respondent. These results suggest that the sun-protection practices of visitors to the Northern Territory are less than optimal, and that among the longer-term residents of the Northern Territory who are at greatest risk of developing skin cancer, precautions against sun exposure could be greatly improved.