Recent work suggests that infertility treatment is associated with adverse child health outcomes. In exploring various methods of assembling a cohort of children conceived by infertility treatment, the authors conducted a validation study of the assisted reproductive technology and infertility drug use check boxes on the Massachusetts birth certificate. Using 2001 and 2002 data, the authors conducted telephone interviews with 399 women whose child's birth certificate had at least one of the boxes checked along with 185 women who were over age 42 years or who delivered twins or higher order multiples to compare the check box information with maternal report. Among the 579 women with available information, the birth certificate was fully concordant with respect to infertility treatment status for 271 (47%) women, partially concordant for 248 (43%) women, and discordant for 60 (10%) women. Agreement between the birth certificate and maternal report was good for singletons (weighted kappa = 0.66) but was found to be very poor among twins and higher order multiples (weighted kappa = 0.05). The authors concluded that birth certificates are an efficient means of locating children conceived with the help of infertility treatment but that they are not appropriate for identifying type of treatment.