A prospective study of pneumococcal infections was performed in cooperation with 40 clinical microbiology laboratories in Germany. Minimal inhibitory concentration (MIC) values for 844 strains of Streptococcus pneumoniae, isolated from patients with systemic infections, were determined in tests with penicillin, tetracycline, erythromycin, chloramphenicol, cefotaxime, and clindamycin by a standard broth microdilution method; 1.8% of pneumococcal isolates exhibited reduced susceptibility to penicillin (MIC, > or = 0.1 micrograms/mL). The Etest, which was used to confirm the level of resistance to penicillin, proved to be a reliable and easily performed method for determination of MICs. The rates of resistance to clindamycin, erythromycin, tetracycline, and chloramphenicol were 1.4%, 3.2%, 11.0%, and 1.9%, respectively. Resistance to cefotaxime was not observed. Typing of a randomly selected subgroup of all strains (n = 115) showed types 1 (9.6%), 14 (8.7%), 3 (7.8%), and 23F (7.8%) to be the most prevalent types in Germany. At least 86.1% of these pneumococcal strains belonged to capsular types included in the 23-valent vaccine.