By homology screening using BLAST searches of expressed sequence tags (ESTs), we have found a previously unidentified cDNA encoding a putative seven-transmembrane receptor with highest similarity to the leukotriene B-4 receptor, BLTR, Analysis of calcium flow in transfected cells, along with sequence analysis, revealed that the EST encoded a functionally inactive protein, lacking the segment corresponding to the C-terminal part of the putative receptor protein. The missing segment was obtained by PCR amplification of a human leukocyte cDNA library and ligated to the truncated EST cDNA, The novel cDNA encodes a full-length receptor with 39% identity to the previously cloned BLTR, Studies of intracellular calcium how of transfected HeLa cells exposed to various leukotrienes showed that also the novel BLTR-like receptor can be activated by leukotriene B-4, and it is therefore tentatively named BLTR2,