OBJECTIVE:To evaluate whether circulating levels of antimüllerian hormone (AMH) predict fecundability in young healthy women. DESIGN:Prospective cohort study. SETTING:General community. PATIENT(S):A total of 186 couples who intended to discontinue contraception to become pregnant were followed until pregnancy or for six menstrual cycles. INTERVENTION(S):None. MAIN OUTCOME MEASURE(S):Fecundability was evaluated by the monthly probability of conceiving (i.e., fecundability ratio [FR]). In addition, circulating levels of LH, FSH, T, and sex hormone-binding globulin (SHBG) were evaluated in 158 of 186 women. RESULT(S):Fifty-nine percent of couples conceived during the study period. Compared to the reference group of women with medium AMH (AMH quintiles 2-4), fecundability did not differ significantly in women with low AMH (AMH quintile 1) (FR 0.81; 95% confidence interval [CI] 0.44-1.40). In contrast, women with high AMH (AMH quintile 5) had reduced fecundability (FR 0.62; 95% CI 0.39-0.99) after adjustment for covariates (woman's age, body mass index [BMI], smoking, diseases affecting fecundability, and oligozoospermia). Irregular menstrual cycles were more prevalent in women with high AMH compared with women with low or medium AMH levels, and they had higher levels of LH (geometric mean: 8.4 vs. 5.3 IU/L) and LH:FSH ratio (2.4 vs. 1.8). After exclusion of women with irregular cycles, women with high AMH still had reduced fecundability (FR 0.48; 95% CI 0.27-0.85) and elevated LH:FSH ratio (2.4 vs. 1.7). CONCLUSION(S):Low AMH in healthy women in their mid-20s did not predict reduced fecundability. Even after exclusion of women with irregular cycles, the probability of conceiving was reduced in women with high AMH.