The present work presents the study of morbidity due to acute respiratory infections (ARI) in areas of the town of Lisa in Ciudad Habana, and Isla Juventud (Cuba), to characterize different aspects of morbidity measured by health care attendance and to measure true morbidity. About 90% of consultations for ARI were first-time consultations, while their ratio to further consultations was 5.3. True morbidity rates (TMR), obtained trough active research, ranged from 110.4 to 163.4 cases per 1000 inhabitants, considerably higher than morbidity rates measured by primary care consultations (MRPCC) in the same time period. The true morbidity index (TMI), as measured by the ratio of the two previous rates, ranged from 5 to 15. A high proportion (47.6%) of cases reported no medical care attendance. These results provide approximate estimates of true morbidity in the study area, and allow the establishment of a new control program, also improving epidemiologic surveillance within primary care activities.