Sets of degenerate oligonucleotide primers synthesized on the basis of the best conserved regions of the chick brain P2Y/P2Y1 and the murine neuroblastoma P2U/P2Y2 receptors were used in polymerase chain reaction experiments on human genomic DNA. An amplified fragment of 712 base pairs was then used as a probe to screen a human genomic DNA library. Several clones were isolated and sequencing revealed an intronless 1122 base pair open reading frame. The corresponding amino acid sequence revealed 83% identity with the chick brain P2Y1 receptor and 34% with the murine neuroblastoma P2Y2 receptor. In COS-7 cells transfected with the coding sequence inserted into the pcDNA3 expression vector, 2-methylthioATP and ATP produced a strong stimulation of inositol phosphates, a typical response of a P2Y1 receptor. Northern blot analysis detected a 6.7 kilobase messenger RNA in most human tissues, the strongest signals being observed in prostate and ovary.