This study has determined long-term continuation rates of clients who attended clinics of the New Zealand Association of Natural Family Planning and became autonomous users. It has also identified factors which might influence the continuation of NFP use. A total of 509 female subjects, 452 of them with their male partners, were enrolled in the study at the beginning of clinic teaching. Once autonomous they were sent questionnaires at 6-monthly intervals for a period of 24 months. Time out was allowed for pregnancy. The number of female subjects entering the 2-year follow-up phase of the study was 406 (79.8%). Of these 164 completed 2 years of use with 102 (20% of study entrants) using NFP and 62 (12.2%) using fertility awareness in combination with a barrier method. Subjects for whom NFP was their first family planning method, who were Catholic or who gave religion as their reason for choosing NFP were more likely to continue long-term use. The majority of subjects (> 90%) were highly satisfied with NFP use, with the most common reasons for satisfaction being self-awareness, freedom from drugs, naturalness and effectiveness. The difficulties reported related to abstinence and cycle interpretation.