Progesterone regulates vital sperm functions such as capacitation and motility; it is also considered as one of the physiological initiators of the acrosome reaction. Progesterone binding and progesterone mediated biological effects are crucial for sperm functions; these are reportedly dysfunctional in a subset of infertile males. Acting through a mechanism independent of transcriptional regulation, the sperm membrane progesterone receptor (PR) demonstrates high structural specificity for the steroid and is unable to interact with progesterone analogs and antiprogestins. At present, the identity of the receptor is unknown; the hormone-receptor interactions are facilitated by albumin and disulphide bonds. Antibodies to the nuclear PR recognize a protein of 55 kDa in sperm lysates that localizes on the acrosomal membrane suggesting the immunological identity of the membrane and the nuclear PR. Decoding the identity of the membrane steroid receptor and understanding the basic cascades of non-genomic mechanisms of progesterone action would be useful in drug designing, targeted towards modifying sperm functions for contraceptive use and for the management of male infertility.