During a period of about one year(November '66 to December '67), the Yonsei University College of Medicine conducted a field trial of the oral contraceptive(Ovulen) in order to study its acceptability and use-effectiveness among IUD drop-outs in Koyang county. We can summarize the outstanding findings from this investigation as follows; 1. 61.4% of the IUD drop-outs interviewed (911 women) wanted to use the pill. Most of the reasons for not wanting to use it(352 women) pertained to either use of other contraceptive methods(98) or subfecundity(150) following IUD terminations. Only 83 out of 911 women gave reasons related to the difficulty of obtaining pills. Therefore, we can state that most IUD drop-outs if still in need of a contraceptive methods are in favor of trying the pill, and especially so if this method is conveniently available. 2. The 467 women or 37% of those who terminated IUD use actually visited the clinic for medical screening, and only 11 of them or 2.4% were rejected because of pregnancy and other medical reasons such as cervical erosion, myoma, breast mass, etc. 5.5% or 25 of the 456 women who received the first cycle did not take a single pill during the study period. 3. When we defined those 431 women who accepted and took one or more tablets we found that women over age 30, with 4 or more children, and/or with a higher educational level were the best prospects for recruitment. 4. In accuracy of use, about two thirds of the users started taking the pill on the 5 th day as directed for the first three cycles, but the percentages rose sharply to about 80% in later cycles. Tardiness in starting pill use in the first cycle may have occurred partly because they had to return to the clinic monthly to get each new cycle. Among acceptors who did not quit between cycles, 80 to 90% were regular users, missing two or less tablets in each cycle. 5) More than 60% of the users felt well and sometimes lost their pre-acceptance symptoms. especially dysmenorrhea. However, 27.4% (58 women) had side effects attributable to the pill compund as nausea, vomiting, indigestion, breast tenderness, decreased lactation or breakthrough bleeding. 25.0% (53 women) also complained of medical diseases or symptoms not related to the pill, especially during the first three cycles. However, as the confidence and experience of the client and the field workers grew, the incidence of unrelated medical complaints quickly fell to a lower level in the later cycles. 6. As of the end of this study, on December 31, 1967, 49.2% (212 women) had discontinued the use of the pill for medical reasons as well as for the non medical reasons. Only one case terminated use due to a pregnancy after taking pills. The cumulative continuation rates (by the life table method), were 58.9%, 51.9%, 41.0% at the end of 3 months, 6 months and one year, respectively. These rates are lower than in the U.S. studies. Even when we add the retaking group to the first segment, the continuation rate goes up only about 5% above the first segment rates mentioned above. Possible explanations are different dosages, the newerness of the method and the use of only one point for pill distribution in the country together with a monthly return for cycle 1, 2, 3, and 4-6.