The leukotriene B-4 receptor (BLTR) is a seven-transmembrane chemoattractant receptor that is important in pro-inflammatory responses. We have produced the first widely applicable monoclonal antibodies against the human BLTR and confirmed the antibody specificity using how cytometric analysis of three different cell lines stably expressing the recombinant receptor. The antibodies did not cross-react with the recently cloned second LTB4 receptor, BLTR2, or the Cys LT1 and Cys LT2 receptors. Functional analysis in combination with two-color flow cytometry showed that the BLTR antibodies bind to cells that are activated by LTB4. The antibodies were shown to recognize BLTR in cell ELISA and immunocytochemistry. Endogenous expression of BLTR in CD15-positive blood leukocytes and in differentiated HL-60 cells was also demonstrated with the antibodies.