The etiology of purulent meningitis was investigated in 109 newborn infants admitted in a neonatal intensive care unit throughout a ten year period. Bacterial pathogens were isolated from the CSF in 57 (52.2%) neonates. There was a predominance of Gram-negative bacilli isolated in 38 (34.9%) neonates. Gram-positive cocci were isolated from CSF in only 12 (11.0%) neonates. Microorganisms associated with nosocomial septicemia and meningitis in neonates--Klebsiella sp, Salmonella sp. Enterobacter sp, Pseudomonas sp, Flavobacterium meningosepticum and Serratia marcescens--were responsible for presumptive etiology in 38 (49.3%) among 77 patients with positive cultures in "closed sites". They were isolated from 22 (57.0%) neonates with prior hospitalization but only from 12 (34.3%) neonates coming directly from their households (chi 2 = 4.08; p < 0.05). The mortality rate was significantly higher in patients with positive CSF cultures (47.4%) in comparison to patients with negative cultures (18.4%) (X2 = 5.01; p < 0.05). It is possible to conclude that Gram-negative bacilli, many of them of hospital origin, are the major pathogens in this study. An improvement on neonatal health care and a scrupulous control of neonatal nosocomial infections are recommended.