The diagnostic value of bacterial cultures from nasopharynx (NPH) was prospectively studied in 261 patients with community-acquired pneumonia requiring hospitalization. NPH culture results were compared with those of other diagnostic methods: Culture from blood and sputum, pneumococcal antigen detection, enzyme immuno assay (EIA) for detection of antibodies against pneumococcal hemolysin and in selected cases bronchoscopy. Pneumococcal pneumonia was diagnosed by these other methods in 121 patients. Streptococcus pneumoniae was detected in NPH in 33 of these patients (27%, or 36% if only cultures obtained before start of antibiotics are considered), but in only four of the other 140 patients. For other species the relevance of NPH culture was uncertain. Because of its simplicity and high specificity NPH culture can be a valuable supplement to other diagnostic methods, particularly when sputum samples are difficult to obtain.