The commercial availability of a 14-valent pneumococcal polysaccharide vaccine justifies repeated investigations of the prevalent pneumococcal serotypes to estimate the probable efficacy of vaccination for patients at high risk of pneumococcal infection. Immunoprophylaxis of infection with S. pneumoniae appears to gain importance since more and more isolates with reduced sensitivity to antibiotics including penicillin are reported. Our investigation of 324 pneumococcal strains, isolated between October 1980 and December 1982 from various clinical sources at the Institute of Hygiene, Cologne, showed that the distribution of predominant serotypes did not differ substantially from that of 1970 to 1972. This distribution resembled closely to those reported from other European countries. However, a lower percentage of the Cologne isolates belonged to the serotypes of the 14-valent vaccine. The potential coverage of the vaccine in our area would probably be in the range of about 60% or less. Determination of the antibiotic sensitivity of the isolates demonstrated resistances against tetracycline, chloramphenicol, and macrolides. Moreover, 1.7% of the strains were "relatively resistant" to penicillin G (MIC 0.125 to 0.25 mg/l). Some isolates were multiply resistant.