The Screening Test of the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III Screening Test) is an individually administered instrument designed to briefly assess the cognitive, language, and motor functioning of infants and young children between 1 month and 42 months of age. The primary purposes are to determine quickly whether a child is progressing according to normal expectations and to determine if further, more comprehensive evaluation is needed. The Bayley-III Screening Test items are a subset of the cognitive, language, and motor items of the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III; Bayley, 2006). The Bayley-III Screening Test can be used to identify young children’s degree of risk for developmental delay and to assist the practitioner in determining whether further evaluation is necessary. By administering the Bayley-III Screening Test, the practitioner can obtain information with which to compare the child to his or her peers in just a few minutes. This approach to assessment enables practitioners to identify challenges early and to recommend interventions at the earliest possible time. The Bayley-III Screening Test is not designed to identify the degree of impairment or specific strengths or weaknesses in cognition, language, or motor functioning, nor should it be used to provide a diagnosis of developmental delay. When in-depth assessment of cognition, language, or motor functioning is indicated by the Bayley-III Screening Test, the full Bayley-III scales should be used to assist in the diagnosis of disorder and to identify areas of relative strength and weakness.