Defective GLUT4 translocation in muscle is a key feature of insulin resistance (Klip et al., 1990; Ryder et al., 2000; Zierath et al., 1996), but to date, defects are assigned to alterations in insulin-derived signals and the possible contribution of proper intracellular sorting of GLUT4 has not been analyzed. The gene discussed is SLC2A4; the disease is Insulin resistance.