A comprehensive evaluation of the present state of infant and preschool mental testing in the United States is the concern of this monograph by the Society for Research in Child Development. Literature, technical and professional, covering the concept of intelligence and its measurement, was reviewed, organized, and summarized (chapters II and III). A questionnaire survey (chapter IV) was made of practices in current testing of infants' and preschoolers' intelligence. Analyses were made of five of the most widely used test scales in terms of actual performances on each test item (chapter V). Conclusions indicate the need for more adequate means of appraising the mentality of young children. The analyses of scale content demonstrated a lack of consistency in the scales now used. More consistent and adequate test scales were recommended. (DO)