The effect of Korean ginseng (ginseng) on spermatogenesis and cAMP-responsive element modulator (CREM) in rat testes was evaluated using sperm analysis, reverse transcription polymerase chain reaction, and Western blot analysis. The ginseng-treated rats exhibited significantly increased sperm count and motility with enhanced levels of CREM messenger RNA and protein. Ginseng appears to induce spermatogenesis via CREM activation in rat testes.