We investigated the expression of the cognate chemokine receptor 1 (CCR1) messenger ribonucleic acid, a G-protein-coupled cognate chemokine receptor with high affinity for RANTES (Regulated upon Activation, Normal T cells Expressed and Secreted), in peripheral blood leukocytes of women with and without endometriosis, and its potential use as a diagnostic test for endometriosis. Because patients with an earlier diagnosis of this disease have a better treatment outcome and a reduced recurrence rate, CCR1 mRNA measurement in the peripheral blood of patients with suspected endometriosis might give us a new perspective in diagnosing and treating this disease earlier and better.