The purpose of the study was to examine reasons for teacher participation in online communities of K-12 teachers. The following research question guided this study: Why do teachers want to participate in self-generated online communities of teachers? These online communities of teachers are communities of practice in online environments. 23 teachers participated in the study. The findings indicated five reasons for participation: (a) sharing emotions, (b) utilizing the advantages of online environments, (c) combating teacher isolation, (d) exploring ideas, and (e) experiencing a sense of camaraderie.