The purpose of this study was to explore factors that influence oral contraceptive (OC) use among women in Iran using the Theory of Planned Behavior (TPB) and concept of self-efficacy (SE). The study sample consisted of 360 married OC users, aged 18-49 years recruited at public health centers of Mashhad, 900 km east of Tehran. SE had the strongest association with the intent to use after the clinic visit (r = 0.784) and with actual use (r = 0.452). Family planning self-efficacy combined with TPB variables accounted for 65% of the variance for intent and 27% of the variance in behavior. The results provide support for a theory-based approach to improved family planning care that specifically addresses more effective use. Development and evaluation of culturally appropriate public education and changes in clinical efforts designed to enhance the sense of SE are discussed.