BACKGROUND: We conducted a nationwide study in the Netherlands to determine cl inical features and prognostic factors in adults with community acquired acute bacterial meningitis. METHODS: From October 1998 to April 2002, all Dutch patien ts with community acquired acute bacterial meningitis, confirmed by cerebrospin al fluid cultures, were prospectively evaluated. All patients underwent a neurol ogic examination on admission and at discharge, and outcomes were classified as unfavorable (defined by a Glasgow Outcome Scale score of 1 to 4 points at discha rge) or favorable (a score of 5). Predictors of an unfavorable outcome were iden tified through logis tic regression analysis. RESULTS: We evaluated 696 episod es of community acquired acute bacterial meningitis. The most common pathogens were Streptococcus pneumoniae (51 percent of pisodes) and Neisseria meningitidis (37 percent). The classic triad of fever, neck stiffness, and a change in menta l status was present in only 44 percent of episodes; however, 95 percent had at least two of the four symptoms of headache, fever, neck stiffness, and altered m ental status. On admission, 14 percent of patients were comatose and 33 percent had focal neurologic abnormalities. The overall mortality rate was 21 percent. T he mortality rate was higher among patients with pneumococcal meningitis than am ong those with meningococcal meningitis (30 percent vs. 7 percent, P< 0.001). Th e outcome was unfavorable in 34 percent of episodes. Risk factors for an unfavor able outcome were advanced age, presence of otitis or sinusitis, absence of rash, a low score on the Glasgow Coma Scale on admission , tachycardia, a positive blood culture, an elevated erythrocyte sedimentation r ate, thrombocytopenia, and a low cerebrospinal fluid white cell count. In adult s presenting with community acquired acute bacterial meningitis, the sensitivit y of the classic triad of fever, neck stiffness, and altered mental status is lo w, but almost all present with at least two of the four symptoms of headache, fe ver, neck stiffness, and altered mental status. The mortality associated with ba cterial meningitis remains high, and the strongest risk factors for an unfavorab le outcome are those that are indicative of systemic compromise, a low level of consciousness, and infection with S. pneumoniae. METHODS: From October 1998 to April 2002, all Dutch patien ts with community acquired acute bacterial meningitis, confirmed by cerebrospin al fluid cultures, were prospectively evaluated. All patients underwent a neurol ogic examination on admission and at discharge, and outcomes were classified as unfavorable (defined by a Glasgow Outcome Scale score of 1 to 4 points at discha rge) or favorable (a score of The most common pathogens were Streptococcus pneumoniae (51 percent of pisodes) and Neisseria meningitidis (37 percent The classic triad of fever, neck stiffness, and a change in menta l status was present in only 44 percent Of the episodes; however, 95 percent had at least two of the four symptoms of headache, fever, neck stiffness, and altered m ental status. On admission, 14 percent of patients were comatose and 33 percent had focal neurologic abnormalities. The overall mortality rate was 21 percent. T he mortality rate was higher among patients with pneumococcal meningitis than am ong those with meningococcal meningitis (30 percent vs. 7 percent, P <0.001). Th e outcome was unfavorable in 34 percent of episodes. Risk factors for an unfavor able outcome were advanced age, presence of otitis or sinusitis, absence of rash, a low score on the Glasgow Coma Scale on admission, tachycardia, a positive blood culture, an elevated erythrocyte sedimentation rtete, thrombocytopenia, and a low cerebrospinal fluid white cell count. In adult s presenting with acute bacterial meningitis, the sensitivit y of the classic triad of fever, neck stiffness, and altered mental status is lo w, but almost all present with at least two of the four symptoms of headache, fe ver, neck stiffness, and altered mental status. The mortality associated with ba cterial meningitis remains high, and the strongest risk factors for an unfavorab le outcome are those that that are indicative of systemic compromise, a low level of consciousness, and infection with S. pneumoniae.