This exploratory study examined the beliefs of 82 experienced Marriage and Family Therapists regarding the treatment of marital infidelity. Participants were asked to read an on-line vignette and respond to a subsequent web based questionnaire by rating levels of hope, threat, forgiveness, and justification for a couple in regard to various affair scenarios. This study employed an experimental design using six groups to discover possible differences in responses across the dependent variables of hope, threat, forgiveness, and justification. Participants were randomly assigned to one of the six groups, which determined which vignette the participant read. The vignettes varied for each group by the type of affair (sexual, emotional, or combination), and the gender of the affair initiator. This study also looked at therapists' personal experience with affairs. Findings suggest an affair initiated by a woman was rated as more threatening to the marital relationship than an affair initiated by a man. Participants were also more likely to justify a woman's affair than a man's affair. While tentative, findings suggest that the type of affair and therapists' personal experience with affairs may be legitimate areas for further study within the context of infidelity research. / Master of Science