Of the 4,480 elderly subjects in a multistage random sampling household survey of a National Survey of the Welfare of the Elderly in Thailand (SWET), 669 (14.9%) reported that they had been hospitalised during the last year and were recruited in an analysis which aimed to examine associated factors of state hospital utilisation among Thai elderly. Seventy eight per cent had been admitted once during the last year. Mean (standard deviation) duration of hospital stay during the last year was 11.9 (20.1) days. For the last period of hospitalisation, 532 elderly (79.5%) were admitted to state hospitals. One hundred and nineteen elderlies (17.8%) used private hospitals. Only 18 elderly (2.3%) used both state and private hospitals. According to the causes of hospitalisation, the elderly who used state hospitals were not more severely ill than those who used private hospitals. Nine univariate factors associated with state hospital utilisation were entered in a logistric regression model in which five independent determinants were identified including 'do not have electricity', 'heads of the family are not their children', 'do not have own savings', 'live in rural area', and 'have heard about free health care programme'. The Ministry of Public Health and organisations which are concerned with the elderly should allocate more resources to advertising a free health care programme for Thai elderly.