The purpose of this randomized, double-masked, placebo-controlled, single-center clinical trial is to determine the efficacy of antimicrobials in young children with acute otitis media (AOM). The primary objectives are to compare time to resolution of symptoms (initial and sustained) in children receiving amoxicillin-clavulanate (90/6.4mg/kg/day in 2 divided doses for 10 days) to children receiving placebo (in 2 divided doses for 10 days), and to compare the weighted average AOM-Severity of Symptoms (AOM-SOS) scores in the two groups during days 1-7. The secondary objectives are to: evaluate the clinical efficacy of amoxicillin-clavulanate vs. placebo at the on-therapy visit (Day 4-5, and at least 72 hours after initial dose of study medication); evaluate the clinical efficacy of amoxicillin-clavulanate vs. placebo at the end-of-therapy visit (Day 10-12); compare AOM-SOS and AOM-Faces scales between treatment groups during each of the first 7 days of therapy and at all study visits; compare the proportion of children in each treatment group who develop worsening symptoms before having received 72 hours of study medication; compare the two treatment groups regarding the quantity of analgesic medication administered by children's parents; compare the incidence of adverse events accompanying the two treatment regimens; compare the effects of amoxicillin-clavulanate vs. placebo on the overall proportion of children with nasopharyngeal (NP) colonization with AOM pathogens (S. pneumoniae, H. influenzae, M. catarrhalis, S. pyogenes), and on the proportion of children with NP colonization with penicillin non-susceptible S. pneumoniae; compare the 2 treatment groups regarding tympanometric outcomes at the on-therapy (Day 4-5), end-of-therapy (Day 10-12) and follow-up (Day 21-25) visits, using an algorithm that permits estimation of the probability of middle ear effusion given any particular tympanographic configuration; compare direct and indirect medical costs between the two treatment groups; and compare parental satisfaction with therapy between the two treatment groups. Participants will include 268 children, aged 6 to 23 months, diagnosed with acute otitis media in Western Pennsylvania. These participants will be recruited into the study at Children's Hospital of Pittsburgh (CHP), Pittsburgh, PA, and Armstrong Pediatrics (Children's Community Pediatrics: an affiliate of CHP) in Kittanning, PA. Subjects will be randomized to receive either amoxicillin-clavulanate or placebo twice daily for 10 days. Parents of the subject will be asked to track symptom status, medication use (study medication and acetaminophen), fever and diarrhea in a study memory aid. Study procedures will include a medical history, vital signs, weight, clinical information regarding signs and symptoms of infection, nasopharyngeal specimens, and a physical exam including tympanometry. Each child will be examined three additional times: 4-5 days after starting the medicine, study day 10-12 and 21-25 days after enrolling in the study. During these visits, study staff will review the child's symptoms and examine the child's ears. The study staff will also obtain a nasopharyngeal culture in order to look for resistant bacteria and to make appropriate changes in antibiotic treatment. Daily telephone assessments will be made by study staff on days 2, 3, and 4 of therapy to make sure the child is getting better. The study staff will see a child anytime a parent feels their child has not improved or has worsened.