The Japanese government approved the use of oral contraception (OC) in 1999, but OC users remain a small minority in Japan. Using the results of an online survey conducted in 2010, I examine the factors determining Japanese women's choice of contraceptive method by estimating multinomial choice models. The estimation results indicate that OC use is positively associated with age, willingness to pay for contraceptive effectiveness, frequency of intercourse and experience with abortion or emergency contraception. These findings suggest that OC use increases as women learn from experience and that the low and declining frequency of intercourse in Japan offers one explanation for the slow diffusion of OC. Additionally, the findings indicate that OC use is more prevalent among women with a higher risk of unintended pregnancies. Subjective probabilities regarding each contraceptive method's contraceptive effectiveness, disruption of romantic moods, partner disapproval, side benefits and minor, non-life-threatening side effects are important determinants of contraceptive choice. The perceived risk levels of OC side effects are significantly higher than the population-based probabilities, implying that increased medical knowledge might increase OC use.