The prevalence of nasopharyngeal carriage of Moraxella catarrhalis was determined for the first time in Cuba. One-hundred fifty healthy children attending three day-care centers in the municipality of Marianao, Havana City were studied. The percentage of recovering bacteria in nasal and pharyngeal swabs was compared. Antimicrobial susceptibilities to ampicillin, trimethoprim-sulfamethoxazole, tetracycline, cefotaxime, ceftriaxone, chloramphenicol, erythromycin, azithromycin, amoxicillin/clavulanate, and norfloxacin were determined by the disk diffusion method according to recommendations of the National Committee for Clinical Laboratory Standards. Sixty-five percent of the children studied carried Moraxella catarrhalis. The nasal cavity was the main isolation site for this organism (81% of positive cultures). Most strains were highly susceptible to the antimicrobial agents tested, except to ampicillin (53.6% resistance). This study provides evidence of the need for continued surveillance of antimicrobial susceptibility of Moraxella catarrhali, in order to determine optimal empiric therapy for community-acquired respiratory tract infections produced by this pathogen.