OBJECTIVE To report cyclosporine and vancomycin disposition during continuous venovenous hemodiafiltration (CVVHD) in a 41-year-old heart transplant patient while in the intensive care unit at a primary and tertiary care teaching hospital. METHODS The patient received a 60-mg infusion of cyclosporine over 24 hours and vancomycin 1 g over 1 hour. Blood samples subsequently were collected and analyzed using whole blood monoclonal radioimmunoassay and fluorescence polarization immunoassay, respectively. Blood samples were measured every hour from the arterial and venous lines of the apparatus, as were ultrafiltrate drug concentrations. Drug clearance rates into the ultrafiltrate subsequently were calculated. CONCLUSIONS Measurements of ultrafiltrate detected no cyclosporine. A slight variation existed between arterial and venous drug concentrations, which was not statistically significant (p > 0.05, paired Student's t-test). Analysis of vancomycin samples revealed a steady decline of drug concentration, with 4.75% of the dose eliminated in the ultrafiltrate. Vancomycin arterial and venous concentrations decreased from 24.4 and 23.3 mg/L to 15.7 and 12.3 mg/L, respectively. CONCLUSIONS Vancomycin is eliminated by CVVHD and it may be necessary for these patients to receive the drug more frequently. In contrast, cyclosporine is not removed effectively by CVVHD; therefore, replacement doses are not warranted.