Purpose: Natural Family Planning (NFP) requires periodic abstinence and partner cooperation to prevent pregnancy. The aim of this study was to learn about the effects of modern NFP methods on marital relationships. Design: Descriptive survey. Methods: Questionnaires were mailed to 1,400 randomly selected couples known to use NFP and residing in the United States of America; 334 couples (24%) responded. Content analysis was used to identify meanings and themes. Numeric analyses were used to determine frequencies. Findings: Nearly two-thirds of the qualitative comments were positive. Four themes were identified in the positive responses: relationship enhancements, knowledge improvements, spirituality enrichments, and method successes. Three negative themes were identified: strained sexual interactions, worsened relationships, and method problems. Although about one fourth of the comments indicated that NFP presented challenges, the majority (74%) found it beneficial, often resulting in stronger bonds, better communication, and improved knowledge. Conclusions: NFP had more positive than negative effects and its use warrants further consideration.