Background: Increased prenatal testosterone exposure has been hypothesized as a mechanism underlying autismspectrum disorders (ASD). However, no studies have prospectively measured prenatal testosterone exposure andASD. The current study sought to determine whether testosterone concentrations in umbilical cord blood areassociated with a clinical diagnosis of ASD in a small number of children and with autistic-like traits in the generalpopulation.Methods: Umbilical cord blood was collected from 707 children. Samples were analyzed for total (TT) andbioavailable (BioT) testosterone concentrations. Parent report indicated that five individuals had a clinical diagnosisof ASD. Those participants without a diagnosis were approached in early adulthood to complete theAutism-Spectrum Quotient (AQ), a self-report measure of autistic-like traits, with 184 males (M = 20.10 years;SD= 0.65 years) and 190 females (M = 19.92 years; SD=0.68 years) providing data.Results: The BioT and TT concentrations of the five children diagnosed with ASD were within onestandard-deviation of the sex-specific means. Spearman’s rank-order coefficients revealed no significant correlationsbetween TT levels and scores on any AQ scale among males (rho range: -.01 to .06) or females (rho value range: -.07to .01). There was also no significant association between BioT or TT concentrations and AQ scores among males(rho value range: -.07 to .08) or females (rho value range: -.06 to .12). Males were more likely than females to have ‘high’scores (upper decile) on the AQ scale relating pattern and detail processing. However, the likelihood of a high score onthis scale was unrelated to BioT and TT concentrations in both males and females.Conclusions: These findings indicate that testosterone concentrations from umbilical cord blood are unrelated toautistic-like traits in the general population. However, the findings do not exclude an association between testosteroneexposure in early intrauterine life and ASD.