We conducted a retrospective study to evaluate an immunochromatographic membrane test (ICT), applied to bronchoalveolar lavage (BAL) fluid samples obtained in patients with suspected pneumonia, for the detection of Streptococcus pneumoniae antigen. The NOW Streptococcus pneumoniae test was assessed on 96 BAL fluid samples. Sensitivity was tested in 20 samples obtained from patients diagnosed as having pneumococcal pneumonia (growth of S. pneumoniae in blood cultures and/or in BAL fluid samples of ≥104 CFU/ml). Specificity was tested in BAL fluid samples of nonpneumococcal etiology ( n = 41) and in samples with no respiratory pathogen and a total bacterial count of