Severity and increasing incidence of serious infections due to Haemophilus influenzae in children have been stressed in recent publications. An analysis of the clinical records of the Department of Pediatrics, Hospital Roberto del Río (Santiago, Chile) was made in order to gather information about frequency and clinical feature of this kind of infections in our environement. 120 children under 3 years of age in whom H. influenzae was isolated in samples of one or more of the following sources: CSF, blood, bone marrow, pleural and synovial fluids, were admitted from January 1970 to March 1976. Among the different syndromes observed, bacterial meningitis (83.3%) was associated with other localizations in 27%. Empyema (12.5%) was often (46.6%) associated with meningitis. Both clinical entities were the most common and with a definite tendency to increase their frequency in last years. Cultures of CSF, blood and bone marrow were considered effective tests for diagnosis in severe infections due to H. influenzae. Although precise incidence figures may not be obtained from the present data, this kind of diseases may be considered frequent and severe (mortality: 26.6% in this study).