The concurrent validity of the Minnesota Child Development Inventory (MCDI) was assessed by comparing the MCDI General Development Scale score and each of the seven area subscale scores to mental age on the Bayley Mental Scale. Subjects were 115 infants (8-30 months old) with suspected developmental delay who were referred to one of two hospitals' pediatric psychology services by their physicians. Correlations were obtained for the entire sample as well as for three chronological age (CA) groups within the sample. Overall validity was supported by significant correlations ranging from 0.75 to 0.91 in the total sample. Variations in the magnitude and patterns of correlations within CA were noted, and suggested groups for which certain scales of the MCDI may be less comparable to the Bayley. Overall results suggest that the MDCI may yield consistent information about the development of infants' skills.