This article describes some of the conclusions reached from an experiment using portfolios for art external assessment at the end of secondary education (age 17+) conducted in five Portuguese schools in 2001-2003. Several positive outcomes were found. Students found portfolios to be motivating and fostering constructive learning, dialogue and co-operation between students and teachers. The new assessment procedures developed communities of assessors enabling some increased consistency of examination results and positive professional development opportunities. However some weaknesses were detected such as potential bias related to the degree of teacher aid and practical problems as, for example, time-consuming in-service teacher training.