Unlike many forms of communication, affection is generally reserved for emotionally close relationships, such as those between romantic partners, close friends, and family members. Affectionate behavior in these relationship categories is explored in this chapter. The chapter begins by revisiting theoretic explanations for why these relationships should differ in their experience and expression of affection. Next, it analyzes empirical research showing how these relationship types differ in their frequency of affectionate communication, and also in their form. Research has also identified a variety of ways in which affectionate communication corresponds with the qualities of those relationships, such as their levels of relationship satisfaction, closeness, love, and intimacy. Some studies show only associations between affectionate expression and relationship quality, but others have demonstrated that increasing affectionate behavior can cause improvements in relationship quality. Both types of studies are also reviewed in this chapter.