We undertook a retrospective study to examine our experience with acute mastoiditis over a 12-year period. Fifty-eight cases were identified in children aged 3 months to 15 years. Acute mastoiditis was the first evidence of otitis media in 54% of our patients. Pain and fever lasting for more than a median period of 4 days were most likely to be the harbingers of incipient acute mastoiditis. Streptococcus pneumoniae was the most common organism recovered from the cultures. All children were treated with intravenous antibiotics; 41 children were managed with an adjunctive drainage procedure. No statistically significant differences were observed between the cure rates and failure rates for children treated surgically with myringotomies with or without tubes and children managed more aggressively with mastoidectomies. One infant had bacterial meningitis. Cholesteatoma was diagnosed in two children. We conclude from our study that acute mastoiditis occurs mainly in young children and may be the first evidence of ear disease. Pain and fever that persist despite appropriate treatment for acute otitis media are the two most important symptoms. Intravenous antibiotics combined with myringotomy with or without tube insertion are as appropriate as intravenous antibiotics with mastoidectomy for initial management of acute mastoiditis in the absence of a subperiosteal abscess or central nervous system extension.