A clinical observation has been made on 500 cases of posttern pregnancy out of 6231 cases delivered at the dept of obstetrica and gynecology, collage of medicine, Ewha womens university for the past 3 years fom Jan. 1, 1983 to Dec. 31, 1985. A pregnancy was considered as postterm when exceeds 42 weeks calculated from the first day of the last menstrual period. The result are as follows: 1) The incidence of postterm pregnancy was 8.02%. Among these 500 cases. 412 cases (6.61%) had 42 gestational weeks. 2) Total delivery in ralation to age distribution showed 3724 cases in 25~29 aged group and 1099 cases in 20~24 aged group while the incidence of postdate pregnancy showed 10.0% in 20!24 aged group and 8.62% in 25~29% aged group respectively. 3) The spontaneous onset of labor in posttem pregnancy was noted in 210 cases (42.0%). 4) Total duration of labor over 24 hours showed 1.12% and 0.63% in primipara and multipara and duration of second stage in labor over 2 hours showed 4.09% and 4.43% in primipara and multipara respectively. 5) The incidence of cesarean section was 30.92% in control group and 36.8% in posttem delivery group. 6) The number of newborn infants weighing 3000~3499 gm were 2447 cases (39.27%) in the control group and 207 cases (41.4%0, more higher in the postdate delivery group. 7) The incidence of the meconium stained amniotic fluid was 21.4% and low Apgar score was more common in meconium stained group. 8) The maternal complications were more common in meconium stained group. 9) The perinated death were 35.94 and 34.0 in control and postterm pregnancy repeatively. The incidence of the perinatal mortality by gestational weeks showed 8 cases for 42 weeks.