The purpose of this study was to compare the effects of two peer assessment methods on university students' academic writing performance and their satisfaction with peer assessment. This study also examined the validity and reliability of student generated assessment scores. Two hundred and thirty-two predominantly undergraduate students were selected by convenience sampling during the fall semester of 2007. The results indicate that students in the experimental group demonstrated greater improvement in their writing than those in the comparison group, and the findings reveal that students in the experimental group exhibited higher levels of satisfaction with the peer assessment method both in peer assessment structure and peer feedback than those in the comparison group. Additionally, the findings indicate that the validity and reliability of student generated rating scores were extremely high. Using Wiki interactive software and providing an online collaborative learning environment to facilitate peer assessment added value to peer assessment. (Contains 3 tables.)