In this publication we present the results of three studies concerning the toxicity and absorption of cerium. In the first experimental study in rats, following the application of a 2.2% solution of cerium nitrate on dorsal wounds for five weeks, delayed healing was demonstrated and histological examination revealed richly vascularized granulation tissue in which microcalcifications and foreign-body type giant cells were found. A high concentration of cerium was found in the liver. The second experimental study employing rat enterocytes demonstrated an immediate cellular toxicity after exposure to a 2.2% cerium nitrate solution. Correction of pH and/or osmolarity did not play a protective role. In the clinical evaluation, significant levels of cerium were found in six blood samples and four urinary specimens, following the application of a 2.2% cerium nitrate solution on burn wounds. Liver biopsies were performed in two cases. There were no abnormal histological findings, but cerium levels were elevated.