This paper repudiates Jensen's hypothesis that differences in IQ scores and scholastic achievement in Negro and white children are genetically based. Specifically, Jensen's identification of IQ scores as a measure of abstract reasoning and problem solving and of levels of ability, and his evaluation of the magnitude of the genetic component in IQ scores, are stated to have raised serious questions. The alternative hypothesis presented is that the distribution of the genetic component in the white and Negro populations both, which Jensen postulated was a reflection of the observed differences in IQ scores, is considered the same in both groups. Using the model from quantitative genetics, it is assumed that the IQ score (the phenotype) can be represented as the sum of two components: (1) that resulting from the genetic structure of the individual (the genotype), and (2) the sum total of all the non-genetic influences (the "environment"). Detailed but simplified mathematical analysis is used to demonstrate that Jensen has omitted consideration of the effects of environmental influence. The need for research on the evaluation of environmental effects involving a wealth of hitherto ignored cultural and psychological factors is emphasized. [Not available in hard copy due to marginal legibility of original document.] (RJ)