This study presents the evidence of reliability and validity for TADI in a sample of Chilean infants and children with Down syndrome (DS), accordingly to international standards. Forty-eight children with confirmed medical diagnosis of DS and their typical peers were matched by chronological age (M = 4,79, DE = 1,7 years). Children with DS were selected using a non-probabilistic procedure and, children with typical development were randomly selected from ELPI's data base (2013). Data was obtained from Test de Aprendizaje y Desarrollo Infantil (TADI), Wechsler Intelligence Scale, third edition-Chilean version (WISC-IIIv.ch.), Leiter International Performance Scale, socioeconomic questionnaire and a survey about the medical condition. The evidence of reliability was stablished via Cronbach's Alpha, the evidence of validity was based on the analysis of content, internal structure and relation with other variables. Results showed good levels of reliability. The evidence of validity shows the content is adequate to explore development, there are not floor or ceiling effects, the internal structure for the group with DS is different from the one reported in the original test and there is strong relation with the external criteria. The professionals should be careful in the interpretation process and future studies must complete these results.