Studies from Norway and Japan have found a higher incidence of medulloblastoma related to births that occur in the fall. The authors sought further evidence concerning this association. For 122 patients in a Duke University database and 90 patients from the Central Cancer Registry of North Carolina, the frequency distribution of birth dates by month was statistically significantly different from the expected North Carolina distribution (p = 0.04 and 0.06). For 75 patients from California Surveillance, Epidemiology, and End Results (SEER) data, the frequency distribution of birth dates by month was marginally different from the expected U.S. distribution (p = 0.14). For 922 patients from national SEER data, the frequency distribution of birth dates by month was not statistically significantly different from the expected U.S. distribution (p = 0.54). Subgroup analysis suggests seasonality of birth dates is most significant for patients aged 5-14 yr diagnosed with medulloblastoma.