A retrospective study was done to evaluate the risk of lumbar puncture-induced meningitis. Fourteen percent (23/165) of patients with bacteremia caused by Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitis, and groups A and B streptococci had spontaneous meningitis (without a preceding lumbar puncture). In contrast, only 0.8% (7/924) of patients with blood culture containing other organisms had spontaneous meningitis and 2.1% (3/140) of these patients had clinical courses consistent with lumbar puncture-induced meningitis. However, the 2.1% incidence in the latter group is not significantly different from 0.8%, the expected incidence of spontaneous meningitis. It is suggested that if lumbar puncture-induced meningitis does occur, it is rare enough to be clinically insignificant.