Previous experiments have demonstrated that insulin receptors emerge upon stimulated lymphocytes while resting lymphocytes lack insulin receptors. The appearance of insulin receptors is totally dependent on RNA and protein synthesis. The results suggest that insulin receptors are synthesized de novo or that new protein is synthesized that is responsible for activation of the receptor. In this study, we investigated the possibility that cryptic membrane receptors are present before lymphocyte activation. As a precedent, hypertonic salt solutions or enzymatic digestion have been reported to uncover cryptic insulin receptors in liver and fat cell membranes. Similar treatment of lymphocytes failed to reveal cryptic, stereospecific receptor sites, although nonspecific insulin binding did increase.