Students in the six-year undergraduate medicine program at UNSW must submit a portfolio which demonstrates inter alia their development in teamwork skills. Much of the feedback they need to develop these skills, as well as the evidence they require to document their achievements, can only come from their peers. The eMed Teamwork system, developed for this purpose, is a computer-based system which gathers feedback from peers in project groups. The feedback submitted to the system is available to the recipient for formative purposes, and becomes part of both the author's and the recipient's portfolios for later summative assessment. This dual use ensures that the feedback is thoughtful and constructive and the system operates without significant moderation by teachers.