Another plausible contributing factor to the trend could be recent changes in administrative policies leading to improved case identification and ascertainment. The federal government, through the US Department of Education,63 first implemented the Education of the Handicapped Act and the Elementary and Secondary Education Act in 1976. The former included 9 categories of educationally related handicaps and the latter included 6 such categories, but ASD was not included in either. In 1978, the laws were made consistent with each other, and multihandicap and deaf or blindness categories were added but not ASD. In 1990, the IDEA supplanted the Education of the Handicapped Act and the Elementary and Secondary Education Act. The following year, in 1991, ASD was added as a specific reporting category in the IDEA, and all states were required to report the number of children with a designated primary disability of ASD who were receiving special educational services. Inclusion of ASD in the IDEA funding and reporting mechanism coincides with the beginning of the upward trend in ASD prevalence observed in Minnesota. In Minnesota, CFL began implementing in 1992 a policy requiring an autism specialist to be included on any IEP team of a child suspected of having an ASD. Then, in 1994, the US government consolidated all federal funding sources for special education into the IDEA, thus becoming the sole funding source for ASD educational services. A grant from CFL in 1997 established a network of regional technical assistance and training projects in Minnesota with the goal of building the capacity of staff, districts, and regions to provide services for young children with ASDs. The focus was on outreach and dissemination of information. Although statistics are not kept by the state on the frequency of use of the Autism Diagnostic Observation Schedule in special educational evaluations, in the past 3 years alone CFL has formally trained 260 educational staff to use the instrument. Therefore, during the 1990s and continuing today, there is a growing italicasis on identification of and services for children with ASD.59 If these efforts represent a major improvement in ascertainment—and our data are consistent with such a conclusion—it appears there has been a substantial underestimation of ASD in the past. Because the IDEA mandates reporting of only the primary disability identified by the IEP team, children with ASD as a "secondary" disability are not included in the statewide statistics. If parents and IEP teams are more likely now than before to classify children with multiple educational disabilities that include an ASD in the ASD primary category, that too may explain some of the observed increase. We cannot quantify the extent to which the changing administrative laws and efforts related to special educational services for children with ASD contribute to the observed pattern of increasing disease prevalence. We can surmise, however, that these phenomena are important contributing factors.