Infidelity has been a common dark-side phenomenon in manufacturer-distributor (M-D) relationships, which, despite its harmful effects on operating performance and long-term viability, has received scant theoretical and empirical attention in marketing research.Using data collected from 103 manufacturers and 101 distributors located in the USA, we investigate this phenomenon by conceptualizing it as a developmental process, comprising motives, symptoms, manifestations, consequences, and remedies. Our findings show that, with a few exceptions, there are no significant differences between manufacturers and distributors with regard to their perceptions of: (a) the structural, processual, and contextual factors contributing to the emergence of infidelity; (b) the behavioral and attitudinal factors helping to diagnose partner infidelity; (c) the ambiguous, explicit, and deceptive manifestations of infidelity; (d) the possible passive, mild, or aggressive consequences of infidelity; and (e) the pre-emptive or post hoc measures that need to be taken to cure infidelity.