Ha-ras expression level in uterine endometrium (EM) in the proliferative phase (PP) was significantly higher than that in the secretory phase (SP). c-myc expressions were detected in EM, uterine myometrium (MM) and uterine leiomyoma (LM) without any cyclic change; fos expressions in LM, MM, and EM were detectable in PP, but not in SP. jun expression level in LM was significantly higher than that in MM and EM in PP, but did not alter during the menstrual cycle. Estrogen elevated the levels of Ha-ras and fos mRNAs in the three tissues, jun mRNA in MM and EM, and c-myc mRNA in LM and MM. These results suggest that there is a tissue difference in the expression of Ha-ras, c-myc, fos and jun among EM, MM and LM, under the influence of estrogen/progesterone.