Age-related macular degeneration (ARMD) is the most common cause of visual morbidity in the aged in the Western world. The aetiology of ARMD is unknown. Although clinicians have noted that ARMD demonstrates a familial tendency, the question regarding the role of hereditary factors in ARMD remains unanswered. The aims of this study were to assess the level of genetic input into ARMD and to assess the mode of inheritance of the disease. Fifty affected patients and 50 age- and sex-matched controls and their immediate families were invited to take part in the study. Thirty-six patients, controls and their families were studied. Eighty-one siblings of affected patients and 78 control siblings were available. Twenty of the 81 affected siblings were found to suffer from ARMD. In contrast only 1 of 78 control siblings had ARMD. This was statistically significant. The results confirm that hereditary factors are important in the aetiology of ARMD.