An investigation has been made into the effects of repeated charcoal hemoperfusion in the rat on liver pathophysiology. Animals underwent hemoperfusion over Norit RBX1 charcoal using a technique which allowed perfusion in the unrestrained and conscious state, thus minimizing any possible effects from stress and eliminating the necessity of repeated anesthesia. Controls consisted of animals subjected to perfusion through empty columns and animals cannulated only. Liver weight, function, and histology were recorded at various times following hemoperfusion and control procedures. The results show that repeated charcoal hemoperfusion is well tolerated in the rat and can be performed safely with no deleterious effects on liver tissue.