Sociodemographic and reproductive health data were gathered on approximately 200 acceptors in each of three programs offering the Ovulation Method of Natural Family Planning. The programs were located in Bangladesh, Kenya, and Korea. In addition, a one year follow-up was attempted to assess continuation and efficacy. Descriptive data show a variety of religious, educational, income, family, and family planning backgrounds among acceptors. Life table analyses of reported unplanned pregnancy occurrence among spacers and limiters combined was 15% at 12 months in Bangladesh, 11% in Kenya and 13% in Korea. The pregnancy rate at 12 months for all pregnancies, planned and unplanned, was 27.0, 26.0, and 23.7, respectively. In Bangladesh 37 of the 48 unplanned pregnancies were user-related as were all of the 14 unplanned pregnancies in Kenya and 17 of the 20 in Korea. Method failure was the reported cause of pregnancy in only 2 of the 83 unplanned pregnancies. A major aspect of this study was the assessment of higher risk population subgroups; increasing age, education, previous pill use and previous family planning are significantly associated with fewer unplanned pregnancies while religion, attendance as a couple, family planning intention, size and source of referral do not have a demonstrated impact on pregnancy occurrence. The time of entry into the data set in relation to time of initial NFP acceptance may be an important variable in assessing OM effectiveness.