During the past few years much effort has been put into simplifying the clinical man-agement of in-vitro fertilization/embryo transfer cycles. One important step was the intro-duction of transvaginal ultrasound-guided oocyte collection, as previously described. This study describes further simplifications in the clinical management of ovarian stimulation and luteal support, and in-vitro fertilization procedure. During the period from October 1994 to September 1995, two major simplification steps were introduced. All cycles were administe-red with a gonadotrophin-releasing hormone agonist according to a long or short protocol preventing premature LH surge. During period Ⅰ(Group Ⅰ, n=62 cycles), closer monitoring by several pelvic ultrasound scans and serum oestradiol was used for monitoring the ovarian stimulation;HTF media with fetal cord serum was used for insemination, growth and tran-sfer media in IVF-ET procedure;progesterine in oil was daily used by intramuscular injec-tion for luteal support. During period Ⅱ(Group Ⅱ-Ⅰ, n=71 cycles), only several ultrasound scans were used for monitoring the ovarian cycle;Medi-cult IVF media containing synthetic serum replacement was used for insemination, growth and transfer media; Progesterine in oil was used daily by intramuscular injection for luteal support. During period Ⅲ(Group Ⅱ-Ⅱ, n=16 cycles), further simplification of the clinical management was introduced by using a intravaginal micronized progesterone(Utrogestan) for luteal support. Retrospective analysis between Group Ⅰ and Group Ⅱ showed no differences in the number of oocyte(13.2±0.8/14.6±1.0), fertilization rate(71.5 %/60.7 %), cleavage rate(63.6 %/57.9 %), number of embryos transfered(5.0±0.5/4.5±0.5). Ongoing pregnancy rates obta ined from the three groups(Group Ⅰ, Group Ⅱ-1, Group Ⅱ-Ⅱ) were 25.8 %, 25 % and 40 %, respectively(p=ns). But introduction of minimal monitoring gave a significant reduction in the average number of US measurements in the simplified groups(Group Ⅱ) compared with the group using the conventional monitoring protocol(Group Ⅰ)(3.8±1.0/8.7±2.8, p<0.05). In the above groups, five patients developed severe OHSS but there was no differenc e in the distribution. Conclusively, simplified protocols including minimal follicle monitoring only by US, IVF-ET with Medi-cult IVF media containing synthetic serum replacement and the luteal support with intravaginal micronized progesterone gave a increased efficacy of the clinical phase of IVF treatment without a reduction in the success rate.