Etiologies of bulging fontanelle and fever and clinical evidence for lumbar puncture were determined from medical records of 153 infants treated at Assaf Harofeh Medical Center, Israel. Age range was 3-11 months (mean 5.6 mos). CSF pleocytosis occurred in 42 (27.3%), including 1 case of bacterial meningitis (0.6%). Other diagnoses were aseptic meningitis (26.7%), URI infection (18.3%), viral disease NOS (15.6%), roseola infantum (8.5%), and acute otitis media (6.5%). Appearance on admission was good to excellent in 113 (73.6%) infants, none of whom had bacterial meningitis. All infants who appeared well on admission had normal clinical, laboratory and imaging studies and non-bacterial disease. Observation and withholding of lumbar puncture are considered appropriate in febrile infants with bulging fontanelle who appear clinically well. 
COMMENT. Bulging fontanelle and fever alone are not always sufficient indication for lumbar puncture. LP is mandatory if these signs are complicated by febrile seizure, toxemia, rash, nuchal rigidity or other signs of meningitis.