Three children were receiving ticarcillin‐clavulanic acid by continuous venovenous hemofiltration (CVVH). Two of them were also receiving concomitant extracorporeal membrane oxygenation (ECMO). We collected ultrafiltrate hourly to determine the clearance of ticarcillin‐clavulanic acid by CVVH. Serum concentrations were also determined at the midpoint of each ultrafiltrate collection. All samples were collected over one dosing interval. The volume of distribution of ticarcillin and clavulanic acid was 0.26. ± 0.01 and 0.69 ± 0.23 L/kg, respectively. Total body clearance of ticarcillin, determined from the elimination rate constant and volume of distribution, was 0.038 ± 0.003 L/kg/hour and for clavulanic acid was 0.18 ± 0.03 L/kg/hour. The sieving coefficients for ticarcillin and clavulanic acid were 0.83 ± 0.11 and 1.69 ± 0.19, respectively. We attempted to estimate the clearances by ECMO, but the result was uninterpretable.