Buyer-seller relationships in the U.S. are changing with the advent of closer, longer-term alliances. In establishing and maintaining these alliances, firms need to understand those factors which determine satisfaction and commitment in relationships. Drawing on theoretical and conceptual work based on Resource Dependence Theory and Social Exchange Theory, this dissertation focused on the buyer-seller dyad in the less-than-truckload segment of the motor carrier industry. The buyer-seller dyads in this segment are particularly interesting since deregulation has necessitated dramatic changes in these relationships. A system of structural equations modeled the determinants of shipper's satisfaction and commitment in these dyads using a correlation input matrix. The network of influencing factors included: carrier's power, shipper's power, comparison level given an alternative and trust. The analysis allowed an in-depth discussion of the relative importance of each of these constructs and found both shipper's power and comparison level given an alternative to have a great influence on satisfaction; satisfaction and trust significantly affect commitment, with satisfaction being more important, relatively speaking. The managerial implications of this research focused on understanding those factors which are most important in creating satisfaction and commitment in buyer-seller relationships. Carrier's need to dedicate personnel to key accounts in order to display initiative in problem solving and responsiveness to inquiries in order to enhance shipper's satisfaction and willingness to commit to a long-term relationship. Other suggested programs include offering customer-oriented programs such as 1-800 numbers, increased flexibility in pick-up and delivery times, and a willingness to forego some accessorial charges.