423 cataract patients and 608 controls between the ages of 50 and 79 were interviewed in a case-control study in Oxfordshire. Diabetes, myopia, glaucoma, peripheral neuropathy and severe diarrhoea were identified as risk factors. The excess risk experienced by females with diabetes was confirmed. The trauma of surgery for glaucoma may be largely responsible for the appearance of glaucoma as a risk factor. Severe diarrhoea has now been identified as a risk factor in England and in India. The risk associated with peripheral neuropathy may indicate a common aetiology at least for some proportions of the two conditions.