Prostaglandins (PGD(2), PGE(2), PGF(2 alpha), and PGI(2)) and thromboxane A(2) (TXA(2)) are biologically active molecules derived from the metabolism of arachidonic acid by cyclooxygenases. They produce a wide variety of physiological and pathophysiological effects mediated through specific G protein-coupled cell surface receptors. In this study, we have mapped the chromosomal positions of the human genes that encode the PGE(2) receptor subtypes (PTGER1, PTGER2, and PTGER3), the PGF(2 alpha) receptor (PTGFR), the PGI(2) receptor (PTGIR), and the TXA(2) receptor (TBXA2R) using in situ hybridization. The PTGER1, TBXA2R, and PTGIR genes mapped to chromosome 19 at positions 19p13.1, 19p13.3, and 19q13.3, respectively. The PTGFR and PTGER3 genes mapped to chromosome 1 at positions 1p31.1 and 1p31.2, respectively, and PTGER2 gene mapped to chromosome band 5p13.1. (C) 1995 Academic Press, Inc.