OBJECTIVE: To investigate the incidence of several common chronic pathologies on the perceived quality of life (PQL) in elderly outpatients (>65years), in Spain, and its possible relation with the consumption of medicines. METHODS: A prospective analysis was carried out, using 1500 questionnaires (Confidence limit >95%; Relative error (+/-) 8%), following a protocol inspired in the OARS design (Duke University). Subjects were chosen following a stratified random design according to the method of proportional fixation (geographical location, age and sex). The survey was carried out by 17 social workers, who received specific training. RESULTS: 21 illnesses were determined, with varying degrees of prevalence in the population studied: arthritis (57.4%); high blood pressure (30%); varicose veins (23.3%); insomnia (21%); heart troubles (17%); bronchitis (14%), and diabetes (12%). Of the more prevalent illnesses which, according to the subjects, those that most affected PQL were heart troubles (70%), bronchitis (68%), arthritis (65%), asthma (60%), diabetes (60%) and insomnia (45%). For all the pathologies, a significant increase in medicine consumption was found in the patients in whom the illness was detrimental to their PQL, as opposed to those who stated that they did not perceive changes in their quality of life owing to the illness. Medicine consumption was reported as follows: high blood pressure (85% vs 22%); diabetes (78% vs 25%)and asthma (72% vs 19%). Neither sex, age nor geographical location affected these results significantly. CONCLUSION: The results obtained show a remarkable increase in the consumption of medicines in the cases in which the pathology and the subjective perception of the illness affected their PQL. The increase was most notable among patients in whom the illness affected their perceived quality of life.