Pharmacokinetics of a parenteral formulation comprised of 5 parts of amoxicillin and 1 part of clavulanic acid were determined in 12 pediatric patients, 2 to 14 years of age. A single dose amounting to 25 mg of amoxicillin and 5 mg of clavulanic acid per kg of body weight was infused intravenously over 2 min. Mean plasma concentrations 5 min after dosing were 89.4 micrograms of amoxicillin per ml and 19.5 micrograms of clavulanic acid per ml. Terminal phase plasma half-lives were 1.2 and 0.8 h, respectively. The data acquired in this study indicate that amoxicillin and clavulanic acid are pharmacokinetically compatible. Moreover, taken with assessment of microbiological activities by others, the present data suggest that intravenous administration of 25 mg of amoxicillin plus 5 mg of clavulanic acid per kg every 6 h is a reasonable starting regimen for assessing the activity of the combined drug formulation in noninvasive childhood diseases caused by Haemophilus influenzae, Staphylococcus aureus, Streptococci spp., Neisseria spp., Branhamella catarrhalis, and other susceptible organisms.