Anal atresia is one of the more common birth defects affecting the gastrointestinal tract. This study examined the relationship between anal atresia and selected demographic and clinical factors in Hawaii. Data were obtained from a population-based birth defects registry and included all cases of anal atresia identified in Hawaii among 1986-1999 deliveries. There were 124 cases of anal atresia, resulting in a rate of 4.38 per 10,000 live births and fetal deaths (95% confidence interval (CI) 3.65-5.23). Cases consisted of 115 (92.7%) live births, 6 (4.8%) fetal deaths, and 3 (2.4%) elective terminations. Chromosomal abnormalities were reported for 10 (8.1%) of the cases, 7 of which were trisomy 21. Family history of anal atresia was reported for 3 (2.4%) of the cases. No secular trend in anal atresia rates was identified (p=0.617). Risk of anal atresia was highest for the 25-29-year maternal age group and lower among younger and older maternal age groups. Risk for anal atresia was lower for females (relative risk (RR) 0.69 95% CI 0.51-0.91) and higher for live births with a birth weight less than 3,000 grams (RR 2.75, 95% CI 2.08-3.56) or less than 38 weeks' gestation (RR 3.90, 95% CI 2.88-5.15) and for multiple births (RR 3.34, 95% CI 1.44-6.57). Anal atresia rates did not vary significantly by maternal race/ethnicity, residence at delivery, gravidity, or prenatal care. Anal atresia risk was associated with maternal age, infant/fetus sex, birth weight, gestational age, and plurality but not maternal race/ethnicity, residence at delivery, gravidity, or prenatal care. Except for maternal age, these findings are consistent with the literature. Copyright 2002 Wiley-Liss, Inc.