This article reports on the design, development and evaluation of an educational virtual environment for biology teaching. In particular it proposes a highly interactive three-dimensional synthetic environment involving certain learning tasks for the support of teaching plant cell biology and the process of photosynthesis. The environment has been evaluated using a sample of 37 in-service teachers. Their attitudes towards virtual reality for educational use were positive. Almost all the teachers managed to integrate the process of photosynthesis inside the virtual cell and answer the relevant questions. One problem was that the teachers were unable to answer questions beyond the certain learning tasks, indicating that any educational software should also involve an integrated approach to the subject under study. (Contains 2 tables and 2 figures.)