STUDY OBJECTIVE: To determine the incidence of cancer among homeless men in Glasgow. DESIGN: Descriptive study of cancer incidence in a defined, though individually unidentifiable, population cohort. SETTING: Glasgow and the West of Scotland Region. PARTICIPANTS: Male residents of 10 hostels for the single homeless in Glasgow, open for all or part of the period 1975-93. Estimated total man-years of risk 21,820. MAIN RESULTS: After adjusting for age and socioeconomic deprivation, the proportional incidence ratio (PIR) of tumours of the oral cavity and pharynx in hostel residents was over twice what would be expected in the male population as a whole (PIR 2.37, 95% CI 1.41, 4.00). Cancers of the oesophagus and larynx were also overrepresented (PIR 1.63 and 1.74 respectively). Estimated age standardised incidence ratios were greater than would be expected for the most socioeconomically deprived areas of the west of Scotland for tumours of the oral cavity and pharynx, larynx, oesophagus, and lung (2.39, 1.87, 1.61, and 1.23 respectively). CONCLUSIONS: The incidence of many cancers is known to be higher in lower socioeconomic groups. Within the lowest deprivation category, there is evidence from this study for a further excess risk among homeless men for cancers of the oral cavity and pharynx, oesophagus, larynx, and lung. Improvements in general health care are urgently needed for this particularly vulnerable section of the population.