Ovulation constitutes an inflammatory-like process, with macrophages migrating into the follicle. This study evaluates the production of two macrophage-specific chemokines, monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-1alpha (MIP-1alpha), in the human follicle at ovulation. Blood samples, follicular fluids and follicular cells were collected during menstrual and IVF cycles. Levels of MCP-1 and MIP-1alpha were measured in follicular fluid, blood plasma and cultured media (granulosa, theca and granulosa-lutein cells [GLCs]). Cells were cultured with or without LH, FSH, interleukin (IL)-1alpha, IL-1beta, tumour necrosis factor (TNF) alpha, progesterone or estradiol. The levels of MCP-1 were markedly higher in follicular fluid as compared with blood plasma in both menstrual and IVF cycles. The difference in MCP-1 levels between follicular fluid and plasma in menstrual cycles increased from the follicular phase (three-fold difference) to the late ovulatory phase (25-fold). Levels of MIP-1alpha were low in plasma and follicular fluid of both menstrual and IVF cycles. Theca cells from follicles of menstrual cycles secreted both MCP-1 and MIP-1alpha under basal conditions, and the secretion was increased by addition of IL-1beta (MCP-1 and MIP-1alpha) and IL-1alpha (MCP-1). GLCs secreted MCP-1 under basal conditions and also MIP-1alpha after IL-1beta stimulation. The macrophage-specific chemokine MCP-1 is highly expressed and is induced by IL-1 in the theca layer of the human follicle at ovulation.