Between January of 1983 and December 1984, 11 strains of pneumococci resistant to penicillin were isolated, from a total of 46 strains studied with clinical signification, thus accounting for 23.9%. In nine cases (19.5%) pneumococci showed partial resistance to penicillin and in two strains (4.3%) resistance was total. Pneumococcal disease in our 11 patients was demonstrated by blood culture in 7 cases and by culture of the CSF, in 4. Diagnosis of the patients were as follows: 4 sepsis in immunosuppressed host, 2 bacteremia without an evident focus, 1 pneumonia, 3 meningitis and 1 ventriculitis. Vancomycin and rifampin are the most active in this cases. Some of the new cephalosporins of the third generation (cefotaxime and ceftriaxone) and cefuroxime have a good activity in vitro and a good passage to the CSF.