Peer evaluations are often used to improve learning in educational settings. As more and more online courses are offered, it is becoming increasingly important to explore new techniques for conducting peer evaluation in online courses. In recent years, wikis have increasingly been used in higher education to support learning and group work. However, the number of studies that discuss the use of a wiki as a peer evaluation tool in online courses is still rather limited. This paper examines the effect of using a wiki as an online peer evaluation tool and identifies the pedagogical benefits and pitfalls of using wikis for peer evaluation activities. It describes a study in which wikis were used as a means to support peer evaluation in an undergraduate online website development course. Students were assigned to groups. Each member performed a peer evaluation of the websites of every other student in the group. At the end of the study, the author surveyed students using an online questionnaire and also examined the information listed on each group's wiki website. The study concludes that wikis are an effective tool for conducting peer evaluation in online courses. A key lesson learned is that website peer evaluations can also be a very strong learning activity for online website development courses--but that the success of this activity highly depends on the people involved in the peer group. Recommendations regarding group formation, coordination, and motivational strategies are offered to assist instructors who are interested in using wikis for their students to perform peer evaluations. Overall, this paper provides some evidence of the ways that wikis can be used to help faculty conduct peer evaluation activities in an online environment and contributes to the body of evidence regarding the use of wikis in online education. (Contains 4 tables and 2 figures.)