Organs perfused in vitro are important experimental models for physiological studies. Perfusion medium supplemented with artificial oxygen carriers would at physiological flow rates supply sufficient oxygen to organs and would be superior to medium containing erythrocytes because it is more defined. Perfluorotributylamine (FC-43), a perfluorochemical, is an artificial oxygen carrier that has been previously reported to be ineffective in maintaining endocrine organs perfused in vitro. The purpose of this study was to determine the efficacy of FC-43 as an oxygen carrier for rat testes perfused in vitro. The effects of FC-43 on testicular function and structure were assessed by comparing the results of experiments using perfusion medium containing either FC-43 or erythrocytes. The results suggest that perfusion medium containing perfluorochemicals must be prepared by standardized procedures and defined as to its physiochemical parameters. The study resulted in the first successful in vitro perfusion of an endocrine organ with perfluorochemicals as oxygen carriers. The results not only provide the basis for an improved perfusion medium but also support in vitro perfused testes as effective experimental tools for testing perfluorochemical-based blood substitutes.