In 2 patients with insulin dependent diabetes and resistance to subcutaneously injected insulin, adequate glucose homeostasis was achieved following the administration of insulin through a subcutaneous peritoneal access device (SPAD). Fasting and post-prandial plasma glucose concentrations fell to near normal levels and HbA1 fell from 17.8% to 9% and from 15.4% to 8% respectively. Insulin requirements fell from 3,000 and 8,000 units to 160 and 100 units per day, respectively. Measurements of sequential free insulin concentrations in serum following subcutaneous and intraperitoneal insulin injection (100 i.u.) showed a significant increase in serum free insulin following intraperitoneal injection, but none after subcutaneous injection. Glucose concentrations fell after intraperitoneal injection of insulin, but not after subcutaneous injection. It is concluded that: intraperitoneal insulin administration is an effective alternative to subcutaneous injections of insulin in patients with this form of insulin resistance; and in patients with this form of insulin resistance, subcutaneous injections of insulin are not followed by an increase in serum free insulin.