The epidemiology of inguinal hernia was investigated in a community survey in a neighbourhood of western Jerusalem in 1969-71. The current prevalence rate, excluding operated hernias, was 18 per 100 men aged 25 and over, and the lifetime prevalence, including operated hernias, was 24 per 100. Prevalence rose markedly with age; the lifetime prevalence rate reached 40 per 100 men at the ages of 65-74 and 47 per 100 at 75 and over. The prevalence of hernia was significantly higher in the presence of varicose veins, in men who reported symptoms of prostatic hypertrophy, and, among lean men only, in the presence of haemorrhoids. These associations may reflect the role of increased abdominal pressure. The prevalence of hernia was low in the presence of overweight or adiposity, suggesting that obesity is a protective factor. No significant age-independent associations were found with chronic cough, constipation, physical activity at work, or a number of other variables. Two-thirds of the hernias had not been operated upon. The prevalence of unrepaired hernias rose with age; 13% of all men aged 65-74 and 23% of those aged 75 and over had unoperated groin swellings. One in every five operated hernias showed evidence of recurrence. No significant age-independent associations were found between evidence of occurrence and other characteristics. A comparison of interview responses and examination findings showed that interview data on the presence of hernias were of low validity, mainly because of under-reporting.