Because of a suspected association between the drug oxymetholone and abnormal glucose metabolism, we determined immunoreactive insulin (IRI) and plasma glucose during oral glucose tolerance testing in seven patients with aplastic anemia, six of whom received oxymetholone therapy. All patients receiving oxymetholone therapy had abnormal glucose and/or IRI values. This finding was independent of GH, cortisol, and glucagon. In one patient, glucose and IRI levels were normal before oxymetholone but became abnormally elevated after the use of this drug. Furthermore, normal glucose and IRI values were present in the single patient not receiving oxymetholone. Thus, a positive relationship was demonstrated between oxymetholone administration and the presence of glucose intolerance and insulin resistance.