Summary The IgG receptor was isolated from a lysate of human cytomegalovirus (HCMV)-infected human fibroblast cell (WI38) by the immunoprecipitation method. The IgG receptor migrated as a single peak in 7.5% of acrylamide gel elec-trophoresis and its molecular weight was 4.2 × 104 daltons. The IgG receptor was identified as glycoprotein and this protein was continuously synthesized at an almost constant rate from the early period of HCMV infection until 72 hr p.i.