The structure of IL-13 receptor (IL-13R) is currently under investigation. Recently, two different human IL-13R chains, termed here IL-13R alpha and -alpha' have been cloned. We have examined various cancer and normal cell lines for the presence of mRNA for IL-13R alpha and alpha, as well as IL-4R p140 (termed beta chain) and IL-2R gamma c chains. In renal cell carcinoma, glioblastoma and ovarian carcinoma (IGROV-1) cell lines, both IL-13R alpha and alpha chains were expressed (type I IL-13R). In epidermoid, colon, ovarian adenocarcinoma (PA-1) and normal mouse fibroblast (COS7) cell lines, only IL-13R alpha' was expressed (type II IL-13R). In hematopoietic TF-1 and EBV-immortalized normal B cell lines only IL-13R alpha' but not alpha chain was expressed along with gamma c (type III or type IV IL-13R). IL-13R alpha' chain was faintly detected in human T cells. All cells expressed the IL-4Rp140 beta chain. These data provide a direct support for our model of IL-13R which consists of three different forms composed of different subunits.