During the 5-year period 1999 - 2003, we treated 36 children with a clinical diagnosis of mastoiditis. Post-auricular tenderness, swelling or abscess was the presenting feature in all cases. Twenty of these children had acute mastoiditis, 12 had acute-onchronic mastoiditis and 4 had a post-auricular abscess and no signs of mastoiditis on mastoid exploration (pseudomastoiditis). No pathogenic organisms were cultured from 25% of cases overall, but among those with positive culture Streptococcus pyogenes and Staphylococcus aureus were the commonest organisms in the acute mastoiditis group and Proteus mirabilis was the commonest in the acute-on-chronic group. In the acute mastoiditis group (20 patients) only 1 patient was successfully treated with antibiotics, the rest requiring cortical mastoidectomy. In the acute-on-chronic mastoiditis group (12 patients) 9 children had cholesteatoma and underwent an open cavity procedure and the other 3, who underwent cortical mastoidectomy, all had positive histology/culture for tuberculosis.