Lumbar puncture (LP) is performed frequently in pediatric emergency departments to diagnose meningitis in infants and young children with fever. Children selected to have LP who do not have meningitis may, however, have other serious bacterial infections. We surveyed lumbar punctures performed in the Boston City Hospital Pediatric Emergency Department and monitored the incidence of meningitis and other serious bacterial infections. Meningitis was diagnosed in 8% of children who underwent LP. An additional 10.5% of children who underwent LP and had normal cerebrospinal fluid had positive cultures of blood (3.1%), urine (4.1%) or stool (3.3%). The decision to perform lumbar puncture identifies children at risk of having not only meningitis but other serious bacterial illnesses. Those children 2 years of age and younger with normal cerebrospinal fluid should be considered for cultures of blood, urine and possibly stool.