This study investigated the effect of similarity and reciprocity on dyadic friendship choices. Subjects were 34 third graders and 30 sixth graders. Reciprocal (mutual) and nonreciprocal (nonmutual) friendships were identified through use of the roster sociometric technique, whereby children choose their three best friends from an alphabetized list of classmates' names. Additionally, popularity and attractiveness scores were obtained, self-concept was measured, and data were obtained on peer interaction and family background variables. It was hypothesized that (1) children in reciprocal dyads would be more similar in verbal intelligence, total self-concept, overall popularity, physical attractiveness, and age than those in nonreciprocal relationships; (2) there would be a higher number of same-sex and same-race friendships in the reciprocal than in the nonreciprocal group; and (3) sixth graders would have more same-sex reciprocal friendships than would third graders. Results revealed that reciprocal friends were more similar in proximity, popularity, attractiveness, and self-concept than were nonreciprocal friends. Sixth-grade dyads were more similar in self-concept and popularity than third-grade dyads. In contrast with cross-sex and cross-race relationships, more same-sex and same-race relationships were found at both grade levels. Results were discussed in terms of social exchange and interpersonal attraction theories. (Author/RH)