In order to determine whether preschool children can successfully identify externalizing symptomatic behaviors (aggression and hyperactivity) in their male classmates, and whether children's perceptions are associated with peer-rated popularity and rejection, 154 preschool boys and girls were interviewed through the use of a peer-nominating procedure. Behavioral data on the preschool boys were also provided by their respective teachers. Results indicated that (1) the peer nominations fulfill the psychometric criteria of interrater reliability, stability, and validity; (2) peer nominations of externalizing behavior correlated significantly with teacher ratings of the same behavior; (3) peer nominations of rejected children correlated significantly with both teacher ratings of, and peer nominations of, hyperactivity and aggression; and (4) contrary to previous findings, the two externalizing dimensions of hyperactivity and aggression were not differentially related to peer popularity and rejection. Additional findings accounting for the inconsistency with previous results are discussed. (Author/RH)