Eighteen patients 2 months to 11 years of age with culture proven bacterial infections were treated with parenteral ticarcillin/clavulanic acid in a noncomparative study. Seven patients had pneumonia, two had tracheobronchitis, three had soft tissue abscess, two had periorbital cellulitis, three had urinary tract infection and one had purulent bursitis. Four of the 18 were bacteremic. Organisms treated included Staphylococcus aureus (6), Pseudomonas aeruginosa (5), Haemophilus influenzae (2), Branhamella catarrhalis (2), Escherichia coli (1), Streptococcus pneumoniae (1), Klebsiella pneumoniae (1), Streptococcus pyogenes (1) and Serratia marcescens (1). Thirteen of 15 (87%) organisms tested were beta-lactamase positive. Therapy was given intravenously in six doses per day at 310 mg/kg. Duration of treatment ranged from 5 to 28 (mean 11) days, with an average time of 4 days to clinical improvement. Seventeen patients (94%) were clinically cured. One patient with recurrent aspiration pneumonia due to mixed infection with multiple gram-negative enteric bacilli failed therapy. Adverse effects were minimal and transient. Notably, mild to moderate thrombocytosis occurred in four (22%) patients that resolved uneventfully. We conclude that ticarcillin/clavulanic acid is safe and effective therapy for serious infections in hospitalized children.