SYNOPSIS We prospectively examined the clinical signs of 54 febrile patients associated with recent-onset headache. They underwent lumbar puncture (LP) on suspicion of meningitis. The relation of each sign to cerebrospinal fluid (CSF) pleocytosis was estimated. Among 34 patients with pleocytosis, 33 had jolt accentuation(sensitivity: 97.1%), while only 5 of them had neck stiffness or Kernig's sign. Among 20 patients without pleocytosis, 12 had no jolt accentuation (specificity: 60%). We found jolt accentuation to be the most sensitive sign of CSF pleocytosis. If jolt accentuation is noted in a febrile patient associated with recent onset headache, the CSF should be examined even in the absence of neck stiffness or Kernig's sign.