AbstractThe effect of nitrous oxide and naloxone, alone and in combination, on female orgasm was investigated. Nitrous oxide enhanced sexual fantasy, whereas naloxone dose—dependency given immediately prior to orgasm—either heightened or diminished sexual pleasure. The bimodal pattern suggests the possibility that the same dual biological system which mediates pain perception may also mediate orgasm. The possible use of nitrous oxide analgesia, with or without naloxone, as a diagnostic, experimental, and therapeutic tool is discussed.