• Thirty children with acute mastoiditis were identified over a 12-year-period and their hospital records were reviewed retrospectively. All had abnormal tympanic membranes and 26 (87%) had swelling above or posterior to the ear that deviated the pinna. Findings on mastoid roentgenograms included clouding (n = 12) and osteitis (n = 7); six were normal. From 13 patients, bacteria were recovered from normally sterile sites and included Pneumococcus (n = 5), group A streptococcus (n = 3), Haemophilus (n = 2), and anaerobes (n = 3). Complications occurred in 13 children, including subperiosteal abscess (n = 7), meningitis (n = 4), osteitis (n = 7), facial palsy (n = 1), and subdural empyema and brain abscess (n = 1). Four of the six children with neurological complications had no external signs of acute mastoiditis on physical examination. Overall, 19 (63%) of the children recovered without mastoidectomy. We conclude that children without meningitis or subperiosteal abscess may be treated initially with antimicrobial therapy plus myringotomy. The need for mastoidectomy should be reassessed in children who fail to respond in 24 to 48 hours.