The Leiden 85-plus study has investigated the prevalence of morbidity in the total population of the Dutch community of Leiden (population 105 000) aged 85 and over, including both independently living and institutionalized elderly. The participation rate of 94% of all living elderly (n = 1037) and 78% of the initial cohort (n = 1259) was exceptionally high. Information was obtained on past and present diseases by taking a medical history. The life-time prevalence for arteriosclerosis and malignancies was 31.9% and 9.7% respectively. High prevalences were found for the non-lethal disabling disorders of hearing and visual impairment (44.4% and 49.9%, respectively) and urinary incontinence (25.6%). The authors conclude that establishing a classical medical diagnosis in the oldest old, which was the goal of this study, is not complete without assessing its effect on the functional ability and the quality of life of the individual.