Maternal vitamin status contributes to clinical spontaneous abortion, but the role of B-vitamin and homocysteine status in subclinical early pregnancy loss is unknown. Three-hundred sixty-four textile workers from Anqing, China, who conceived at least once during prospective observation (1996-1998), provided daily urine specimens for up to 1 year, and urinary human chorionic gonadatropin was assayed to detect conception and early pregnancy loss. Homocysteine, folate, and vitamins B6 and B12 were measured in preconception plasma. Relative to women in the lowest quartile of vitamin B6, those in the third and fourth quartiles had higher adjusted proportional hazard ratios of conception (hazard ratio (HR) = 2.2, 95% confidence interval (CI): 1.3, 3.4; HR = 1.6, 95% CI: 1.1, 2.3, respectively), and the adjusted odds ratio for early pregnancy loss in conceptive cycles was lower in the fourth quartile (odds ratio = 0.5, 95% CI: 0.3, 1.0). Women with sufficient vitamin B6 had a higher adjusted hazard ratio of conception (HR = 1.4, 95% CI: 1.1, 1.9) and a lower adjusted odds ratio of early pregnancy loss in conceptive cycles (odds ratio = 0.7, 95% CI: 0.4, 1.1) than did women with vitamin B6 deficiency. Poor vitamin B6 status appears to decrease the probability of conception and to contribute to the risk of early pregnancy loss in this population. Alemán