Salesperson cooperation has become a crucial issue for the overall performance of most sales organizations. The authors examine the antecedents of task-specific, cooperative behaviors of salespersons toward other salespeople working in the same organization. The main theses of the study are that (1) the four major antecedent categories of factors - relational, task, organizational, and personal - constitute, collectively, the primary determinants of salesperson cooperation and (2) each antecedent category exerts, independently, significant influence on the cooperative behaviors of salespersons. The results support the main theses and provide useful insights for sales managers attempting to foster cooperation among salespeople. The relative impact of each antecedent category, as well as the effects of specific variables within each, is discussed.