In accordance with the progress of recent angiography, the origin and the course of the internal iliac artery in the pelvic cavity are very important in the areas of gynecology and urology. Using 50 Japanese female fetuses (6-10 months) , the branching of the internal iliac artery was investigated from a clinical standpoint. The main findings are as follows: 1) In most cases the common iliac artery arose at the part of the 4 th lumbar: 33/42 (78.6%) . 2) In 34.9% of the cases, 15 cases out of

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... cases, the right common iliac artery was longer than the left one, and in 53.5%, in 23 cases the left side artery was longer than the right one. 3) The origin of the internal iliac artery mostly situated at the 5 th lumbar: 27 out of 48 cases (56.3%) on the right side. 27 out of 47 cases (57.4%) on the left side. 4) The dividing patterns of the internal iliac artery are classified into 4 groups and 10 types. II-I was the most popular type, 49 out of 99 cases (49.5%) . Namely, the superior gluteal artery arose independently as the first branch, then the 2nd branch arose forming a common trunk together with the inferior gluteal artery and the internal pudendal artery. 5) One iliolumbal artery was found in all the cases on the left side and 48 cases out of 50 cases on the right side. In most cases, the iliolumbal artery arose directly from the internal iliac artery: 40 out of 53 cases (75.5%) on the right side. 37 out of 49 cases (75.5%) on the left side. 6) Two lateral sacral arteries were most commonly found on both sides: 50 out of 99 cases ( 50, 5%) . Mostly, in 83.0% cases, it arose from the superior gluteal artery. 7) Two cases of two uterine arteries were found out of 98 cases. 96 cases arose from the internal iliac artery. In 90% of the cases, the original position of the uterine artery from the internal iliac artery on the right side was found to be at the middle to the upper wall and in 85.5% of the cases it was at the middle to the lower part of the wall on the left side. 8) Two obturator arteries were found: 7 out of 99 cases (7.1%) . In most of the cases (49 out of 106 cases, 46.7%) , they arose from the internal iliac artery directly as an independent branch. The branches of the obturator arteries in all the cases were connected with the inferior epigastric arteries or the external iliac arteries. 9) One to six superior vesical arteries were most commonly found: 92 out of 98 cases (93.9%) . Most of them arose from the internal iliac arteries directly as independent Lbranches: 317 out of 361 cases (87.8%) . 10) One to two inferior vesical arteries were most commonly found: 89 out of 98 cases (90.8%) .