Parents of children with autism spectrum disorders (ASDs) may elect to use complementary and alternative medicine (CAM) treatments with their children in place of, or in addition to, conventional treatments. CAM treatments are controversial and understudied and, for most, the efficacy has not been established. The current study (n = 248) examined reports (via an internet survey) from parents of children with an ASD, asking of CAM usage, recommendation sources, expectations, costs, parent-rated assessments of efficacy, and reasons for stopping use of CAMs. Over 70% had tried at least one CAM treatment with their child, and about half were currently using one or more CAMs. Parents entered treatment with high expectations, although they varied considerably in their assessment of whether CAMs helped their child. Odds ratios of parent-rated efficacy give small leaning toward improvement over non-improvement for CAM treatments. The findings highlight the need for methodologically sound research on CAM treatments. Also needed is dissemination about treatment efficacy to help parents and professionals make educated judgments regarding both CAM and routine interventions. (Contains 6 tables.)