We report on the development in Argentina of a screening questionnaire for autism administered over the telephone. The Autism Diagnostic Inventory-Telephone Screening in Spanish (ADI-TSS) is based on the Autism Diagnostic Interview-Revised (ADI-R), keeping its structure but including fewer questions, which were rephrased to assess them over the telephone. The ADI-TSS went through different versions, with each modification gaining in reliability. The final version of the ADI-TSS could be assessed in 20 to 40 minutes and demonstrated a high validity (using the ADI-R as the diagnostic gold-standard), high intrarater and interrater reliability (as measured with intraclass correlations), and high internal consistency (as measured with Cronbach's alpha). The validity of the ADI-TSS remained high when used by a health-related professional without formal training in the assessment of autistic patients. We believe the ADI-TSS is useful in field research studies as a screening instrument for patients with a potential diagnosis of autism, although future validation studies should include larger samples.