This paper describes the development of a practical, which is taught to third year biotechnology students. We wanted to motivate the students by making them responsible for a research project. Competition was added as a stimulus for interaction between the students. A virtual company called CaroTech employed the students for 2 weeks. They worked in groups of two persons and each group was responsible for a 0.8 1 flat panel photobioreactor. They had to produce as much beta-carotene as possible using the marine alga strain Dunaliella salina in this photobioreactor. On the first day, students developed a strategy to obtain optimal algal growth rate. They putted this plan into practice the second day and while cultivating the organism, they developed a second strategy how and when to stress the alga to initiate beta-carotene production. At the end of the ninth day, the total amount of beta-carotene was measured. To stimulate competition, the group that produced the most beta-carotene obtained half a point bonus on the final practical mark. On the tenth day, each group presented their results and an evaluation of their chosen strategies to the CaroTech board. Most groups were successful in growing algae. In the second phase some groups failed to stress the alga. The best group produced more than two times beta-carotene than the runner-up. The students were motivated by being responsible for their own results and the competitive approach. All students liked the practical and indicated that they learned a lot by following this practical. (C) 2003 Elsevier B.V. All rights reserved.