Examined the shared and unique contributions of low cognitive ability and inattention to the development of social behavior problems and peer relationships of children at the time of school entry. Kindergarten and first-grade assessments of cognitive ability, inattention and prosocial and aggressive behavior were collected for a multisite, normative sample. Sociometric assessments of peer relationships were collected at the end of first grade. Cognitive ability and inattention both contributed to the prediction of social behavior and peer relationships. Low cognitive ability was particularly predictive of prosocial skill deficits, and social behavior mediated the relation between cognitive ability and social preference. Inattention predicted both prosocial skill deficits and elevated aggressive-disruptive behavior problems. Behavior problems partially mediated the relation between inattention and social preference. Identified subgroups of children with elevated levels of inattention or low cognitive ability showed different patterns of peer problems, with low acceptance characteristic of the low cognitive ability (only) group and high dislike ratings characteristic of the inattentive and inattentive/low-ability group. Implications are discussed for the design of early intervention and prevention programs.Children with learning problems, including those identified as learning disabled (McConaughy & Ritter, 1986;Nabuzoka & Smith, 1993), developmentally delayed (Guralnick & Groom, 1987) and low-achieving (Green, Forehand, Beck, & Vosk, 1980;Taylor, 1990), often experience problems gaining acceptance and avoiding rejection by peers. Poor peer relationships, in turn, predict serious difficulties in later life, including truancy, antisocial behavior, social anxiety, and an increased need for mental health services (Parker & Asher, 1987). Peer relationships provide an important context for the development of basic social Requests for reprints should be sent to Karen L. Bierman, Department of Psychology, Pennsylvania State University, 522 Moore Building, University Park, PA 16802. kb2@psu.edu. Christine Bellanti is now at Bradley Hospital, Brown University School of Medicine. 1 Members of the Conduct Problems Prevention Research Group (CPPRG), in alphabetical order, are Karen L. Bierman, Pennsylvania State University; John D. Coie, Duke University; Kenneth A. Dodge, Duke University; Mark T. Greenberg, Pennsylvania State University; John E. Lochman, University of Alabama; Robert J. McMahon, University of Washington; and Ellen Pinderhughes, Vanderbilt University.Publisher's Disclaimer: Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation ...