Thiamin is one of the marginally adequate nutrients in the Australian diet. The incidence and prevalence of Wernicke-Korsakoff syndrome in this country may be the highest in the world. Homeless men could be at risk for low intakes of thiamin in association with irregular high alcohol intakes. A sample of 107 homeless men from two hostels and one clinic for homeless persons in inner Sydney was investigated for nutritional status; their thiamin status is reported here. By means of 24-hour recall methods, their mean dietary thiamin intake--0.76 mg per day--was less than the National Health and Medical Research Council's recommended dietary intake of 1.1 mg per day; at 0.076 mg/MJ it was even less than the minimal requirement of 0.08 mg/MJ. It was much lower than the mean intake of 1.38 mg per day that was found in the 1983 National Dietary Survey of adults and the distribution of thiamin intakes in this study was skewed positively, with the largest intake being in the range of 0-0.1 mg per day. On clinical examination we found a high prevalence of signs that were consistent with thiamin deficiency. Twenty-four per cent of the subjects showed three-or-more of the signs of the Wernicke-Korsakoff syndrome (ophthalmoplegia, nystagmus, ataxia, peripheral neuropathy and global confusion). In assaying for red-cell transketolase levels, this subgroup showed higher thiamin pyrophosphate effects than did the whole sample. Thirty-six per cent of the whole sample showed subnormal thiamin status by the thiamin pyrophosphate effect. Thus, in this sample, homeless men showed a high prevalence of dietary, biochemical and clinical features to indicate subclinical or early clinical thiamin deficiency.