The hypothesized influence of a best friend's educational and occupational aspirations on the formation of ego's aspirations and the reciprocal influence in the opposite direction can be represented in path diagrams and equation systems involving simultaneous or jointly dependent variables. Standard methods of path analysis may be extended along lines suggested by work in econometrics to secure estimates of coefficients when the models are just identified or overidentified. The most plausible interpretation was reached with a model postulating an underlying factor, "ambition," that is involved in such reciprocal nifluences and accounts for the correlations among the observed indicators, educational aspirations and occupational aspirations. Homophily with respect to background characteristics does not fully explain homophily with respect to ambition; a path coefficient of about 0.2 runs from friend's to respondent's ambition, and one of equal size runs in the opposite direction.