Surveys to determine the scope of compliance with the law requiring seat-belt use in Thailand were conducted by observation and interviews with drivers in four cities: namely, Bangkok Metropolis, Chiang Mai, Phuket and Nakhon Ratchasima. The work was carried out in two separate sessions: during the first month following enactment of the law, and six months after its enactment. The sample comprised 46,949 vehicles in the first session (January 1996) and 76,188 vehicles in the second session (July 1996). The results showed that 42.7 per cent of drivers used seat-belts in January and 30.7 per cent in July. When the data were disaggregated according to cities, it was found that more Bangkok drivers complied with the seat-belt law than in Phuket, 24.6 per cent; Chiang Mai, 22.1 per cent; and Nakhon Ratchasima, 18.3 per cent relatively low compliance rate was encountered among drivers of pick-up trucks (including those with modified roofs) and vans, particularly farmers and the self-employed. Women drivers tended to abide by the law more often than men (OR = 1.7, 95% CI = 1.12, 1.23). Inter-city travelers wore seat-belts more than those traveling in the city (OR = 1.74, 95% CI = 1.68, 1.80). About one-fifth of non-users or those who rarely used seat-belts were unsure of the effectiveness of seat-belts in preventing serious injury or death in the case of an accident. Discomfort associated with using seat-belts and the perception that they were rendered unnecessary because of slow traffic in cities were other reasons for non-compliance in 50.6 per cent and 43.9 per cent of cases, respectively. The decline in compliance with the law six months after its enactment indicates that there may be a problem with uniform and consistent enforcement of the law.