In a prospective, open, randomized trial, ceftazidime was given to 15 children and aztreonam to another 15 children with chronic suppurative otitis media without cholesteatoma (CSOM). Patients enrolled to the study had a pure culture of Pseudomonas aeruginosa growing in middle ear discharge. The subjects' mean age was 56 months in the ceftazidime group and 48 months in the aztreonam group. Success rate, defined as complete disappearance of discharge, was 84.6% in the ceftazidime treated patients and 67% in the aztreonam group (p value not significant). The number of days required for complete dryness of the ear was 7.9 and 8.4 respectively. Two patients in each group had recurrence of suppurative discharge within 90 d from discontinuation of antibiotic treatment. These results suggest that aztreonam is an optional alternative systemic treatment for paediatric patients with pseudomonal CSOM, especially in subjects allergic to penicillin.