Based upon the PREP scoring system, retrospective clinical analysis was attempted on 145 cases of spontaneous preterm delivery which had occurred during the period of 22 months from September, 1, 1982 to June, 30, 1984. The results obtained were followings: 1. The incidence of spontaneous premature delivery was 5.9% and early perinatal death was 35.2%. About two third(62.2)% of all perinatal death occurred in premature group. 2. The malority(92.4%) was belong to PREP score 11 or more and only 7.6% was in PREP score 10 or less. 3. The relationship between the last PREP score and newborn weight, and that of gestational weeks showed slight inversed tendency, respectively. 4. The predictable value of PREP score system seemed to be higher in primipara than multipara if the PREP score were under 20. 5. The relatively important constant risk factors were previous curettage, 2nd trimester abortion, preterm delivery, low socioeconomic state and short pregnancy interval. 6. The most important variable risk factors were uterine contraction and dilatation of cervix, and other factors were in order of unsuitable living quarters, poor weight gain, signs of preeclampsia, and anemia. 7. The causes of spontaneous preterm labor were in order of PROM(34.5%), unknown(24.1%), previous preterm delivery or late abortion (11.7%), faulty placentation (10.3%), and twin or hydramnios(7.6%).