The Vineland Adaptive Behavior Scales is an extensive revision of the Vineland Social Maturity Scale; however, research comparing the two scales with different populations and measures of intelligence is limited. The Vineland Adaptive Behavior Scales--Survey Form, the Vineland Social Maturity Scale, and the mental scale of the Bayley Scales of Infant Development were administered to 44 infants referred for evaluation of developmental delay. The differences between means were compared and shared variance examined. The Vineland Adaptive Behavior Scales--Survey Form scores were significantly higher than those of the Vineland Social Maturity Scale and the Bayley Mental Development Index. No significant differences were found between the means of the Vineland Social Maturity Scale and the Bayley Scales of Infant Development--Mental Development Index. Correlations were .59 between the Bayley Index and scores on the Vineland--Survey Form and .72 between the Bayley Index and the Vineland Social Maturity Scale. Between versions of the Vineland scale r = .39. Implications for diagnosis and educational classification are discussed.