This study examined the prevalence of the use of different types of conventional, complementary and alternative therapies by children diagnosed with an autism spectrum disorder (ASD). Of 112 families surveyed, 74% were using complementary and alternative medicine (CAM) for their child with ASD. CAM use was most strongly associated with parent report of child's diagnosis. Most CAM was reported by families to be either helpful or without effect, but not harmful. The main reasons for choosing CAM were related to concerns with the safety and side effects of prescribed medications. Conventional health care providers should be aware of the high prevalence of use among children with ASD and be prepared to discuss the use of CAM with families.