Glycogen was quantified in rat adipocytes by isolation using conventional KOH digestion and ethanol precipitation, followed by hydrolysis and spectrophotometric assay of the glucose product. A concentration of 0.193+/-0.020 micromol glucosyl units/10(6)cells was recorded. When this procedure was modified by including a 4h incubation with glucose oxidase prior to glycogen hydrolysis, the glycogen concentration was found to be 0.055+/-0.008 micromol glucosyl units/10(6) cells. Therefore in adipocytes, conventional glycogen assays give substantial overestimates due to incomplete removal of glucose during glycogen isolation. Contaminant glucose can be scavenged in a simple manner by incubation with glucose oxidase prior to glycogen hydrolysis.