This study examines the linkage between dose heterosexual relationships and their social networks of dose friends and family members. The central proposition of this study states that relational development will be positively associated with each partner's involvement in the other's social network and the degree of overlap in the individual social networks of each partner. Generally, the findings were consistent with this proposition. Among the indicators of network involvement and overlap, the range of network involvement (i.e., number of known members in the partner's network) emerged as the most powerful predictor of relational development. Findings are reviewed in light of existing theories and research, and suggestions for future research are made.