Although teratoma is the most common type of neonatal tumour, there are few population-based epidemiological data on teratoma among infants. Using data from a population-based birth defects registry in Hawaii, this study described the distribution of teratoma with respect to various demographic and clinical factors. A total of 22 cases were identified among deliveries in 1986-2001, of which 13 (59.1%) were located in the sacrococcygeal region. The rate per 10 000 live births was 0.74 for all cases and 0.43 for sacrococcygeal cases. Major birth defects were identified in 7 (31.8%) of the cases. Females accounted for 57.1% of all cases and 58.3% of sacrococcygeal cases. Teratoma rates were highest for Pacific Islanders (1.08) and lowest for Far East Asians (0.37) and Filipinos (0.72). The rate was higher in metropolitan Honolulu (0.89) than in the rest of Hawaii (0.62). Teratoma rates were greater with gestational age < 38 weeks (2.15) than for gestational age >or= 38 weeks (0.34). No clear differences in rates were identified with respect to maternal age, birthweight and plurality. Except for gestational age, the rate differences were not statistically significant. In conclusion, this study found that most of the teratomas among infants occur in the sacrococcygeal region. Differences in teratoma rates were noted with respect to sex, maternal race/ethnicity, geography and gestational age. Due to the small number of cases, caution should be used when interpreting the results. Further investigation involving larger data sets is recommended.