The ability of latex agglutination (Slidex Pneumokit) and counterimmunoelectrophoresis to detect Streptococcus pneumoniae antigen in body fluids was evaluated. The patients were classified as having proven Streptococcus pneumoniae infection, suspected Streptococcus pneumoniae infection, acute superinfection of chronic bronchitis or non-pneumococcal respiratory infection. Sixty-two non-pneumococcal meningitis patients were also included in the study. Latex agglutination and counterimmunoelectrophoresis tests were performed on serum, urine and cerebrospinal fluid specimens when indicated and repeated each week until the patient was discharged. Latex agglutination was done on samples boiled for 10 min. In vitro sensitivity of counterimmuno-electrophoresis and latex agglutination were 10 and 1 ng/ml respectively for type three antigen. In pulmonary disease (proven and suspected Streptococcus pneumoniae infection) counterimmunoelectrophoresis and latex agglutination had a clinical sensitivity of 72.9 and 87.5% respectively, a specificity of 96.3 and 92.6%, a predictive value for a positive test of 97.2 and 95.4% and for a negative test of 66.6 and 80.6%. Latex agglutination may offer an alternative to counterimmunoelectrophoresis in the rapid diagnosis of Streptococcus pneumoniae infections since it is easier to perform and gives a reliable result within 15 min.