When we teach a subject we hope that students will gain information, acquire experimental skiJls, learn how to plan experiments and interpret data, become adept at problem-solving, and develop a wider vision so that they can generalize about an area of knowledge. The ways in which we teach usually include lectures, practical cla.ues and/or 'dry labs', and tutoriala or seminars. In addition, we may use audio-tutorials and computer- &Histed instruction, and we will certainly expect the students to study independently from textbooks, published papers and reviews. Much has been written about the aims of l~s, but there are doubts, frequently expressed, that lectures are not very effective aa instruments of either long-term or short-term learning. Nevertheless lectures remain. and are likely to remain, a major instrument in our teaching for a variety of reasons, not all of them (00d ones. Many of us use tutorial teaching to 'correct' students misconceptions that result from misunderstanding lectures or textbooks.