The broad autism phenotype (BAP) refers to the phenotypic expression of an underlying genetic liability to autism, manifest in non-autistic relatives. This study examined the relationship among the Broad Autism Phenotype Questionnaire (BAPQ), Social Responsiveness Scale: Adult Research Version (SRS:ARV), and Family History Interview (FHI) in a large, multi-site study of 1,650 simplex families (Simons Simplex Collection). Correlations between the BAPQ and SRS:ARV Total scores were moderate, and correlations between FHI ratings and SRS:ARV and BAPQ were significant but weak. Overall, the results suggested that BAP traits occur at low rates in simplex families, and rates vary significantly depending upon the measure utilized. Implications include the need for multiple informants, and the assessment of distinct BAP traits in large-scale genetic studies of individuals with ASD.