The second component of friendship patterns is friendship processes, which encompass cognitive, affective, and behavioral categories as well as proxy measures. This chapter includes a review of research on various friendship processes at three stages of the adult life cycle, followed by a comparison of processes across genders and the life course. Although interaction processes have been studied widely in laboratory experiments among people meeting for the first time and in ongoing romantic relationships, relatively little research on the operation of processes in friendship exists. Moreover, the various processes have not been studied comprehensively across age groups or with the same measures, so for the most part it is not possible to compare specific processes of college student, adult, and old-age friendships. ...