Human insulin receptors have been partially purified from cultured diploid fibroblasts and from erythrocytes. Cell membrane fractions were prepared by differential centrifugation and solubilized with Triton X-100. Gel filtration chromatography of the 45,000 x g pellet yielded a single sharp peak of binding activity with an apparent molecular weight of 370,000. Solubilized receptor preparations showed binding affinity, pH optimum, and analog specificity similar to those for whole cells. These data indicate that insulin receptors may be isolated from readily obtainable normal human cells. In the case of the fibroblast, the system has the potential for the coordinated study of insulin receptor biochemistry and insulin action.