Thirty seven infections due to "Haemophilus influenzae" b were registered from January 1979 to December 1983. The organism was isolated from blood and/or CSF in all cases. Relation with sex or season predominance was not observed. Children's age was 1 day to 9 years, 83% were below 2 years. They were 16 meningitis (43.2%); 10 pneumonias (27.0%); 4 epiglottitis (10.8%); 4 bacteremias; 2 perinatal infections and 1 case of arthritis. Six cases (16.2%) were hospital infections. Age for meningitis and pneumonias was significantly lower than for epiglottitis. Eight strains were ampicillin resistant (21.6%). In meningitis 31.1% and in pneumonias 30.0% of the strains were resistant. There were no resistances in other localizations. One strain resistant to both, ampicillin and chloramphenicol was treated with cefotaxim.