Marital infidelity is present in many marriages and can have a strong impact on the couple, from feelings of anxiety to symptoms of stress. Clinical work and dialogue with couples show that marital infidelity arises as a result of several factors related to the dynamics of the couple. However, marital satisfaction is multifactorial, related to the personality of the subjects, extrafamilial relationships, communication within the relationship, the way conflicts are created and managed. This book proposes to address not only the spouse who practices infidelity to the marital relationship, but the couple itself. It is hoped to offer the reader, through this literature review, a profile composed of some characteristics of couples, who have incurred in acts of marital infidelity. Concrete clinical cases discussed and approached within the systemic approach will be presented, as well as a case study of the wife who practiced marital infidelity, in order to realise that cases of infidelity in contemporary times are no different from those that occurred in the 1990s, a period demonstrated in clinical reports.