The Cognitive Adaptive Test/Clinical Linguistic and Auditory Milestone Scale (CAT/CLAMS) was designed for use by primary pediatric health care providers to identify children with developmental delays. This study assesses the concurrent and predictive validity of CAT/CLAMS developmental quotient (DQ) scores and the Mental Developmental Index (MDI) of the Bayley Scales of Infant Development in healthy children without risk factors for developmental delay. Overall CAT/CLAMS DQ scores correlated significantly with Bayley MDI scores at both 12 (r = 0.393; p = 0.008) and 30 months (r = 0.742; p = 0.0001) of age. Overall CAT/CLAMS DQ scores at 12 months of age also correlated modestly with Bayley MDI scores at 30 months of age (r = 0.181; p = 0.036). Despite its modest predictive validity at 12 months, its satisfactory concurrent validity plus its ease and speed of administration make the CAT/CLAMS a reasonable choice for assessment of early development by primary pediatric health care providers.