We have isolated and sequenced a 1.3 kilobase (kb) cDNA that contains the entire 804 base pair coding region of the murine interleukin 2 (IL 2) receptor. A comparison with the human IL 2 receptor sequence revealed regions of high conservation, including the short (11 amino acid) intracytoplasmic domain, as well as an internally repeated sequence that is consistent with the receptor containing at least two distinct extracytoplasmic domains. When inserted into the expression vector pcEXV-3, this cDNA directs functional membrane expression of the IL 2 receptor on transfected COS 7 cells. An analysis of cytoplasmic RNA from IL 2 receptor-bearing T cells reveals five distinct polyadenylated transcripts ranging in size from 1.7 to 4.7 kb. All five transcripts are evident in both concanavalin A-stimulated splenic T cells and in the IL 2-dependent line CTLL. Some of this size heterogeneity is due to different sites of polyadenylation, resulting in mRNAs that differ in the 3' untranslated region. We cannot exclude the possibility of alternative splicing, however, which may result in distinct forms of the IL 2 receptor on the cell surface.