Large-scale cognitive-behavioural Stress Management workshops were run for members of the general public as part of a city-wide mental health promotion campaign. Four groups were compared: a workshop run over one day (Full-Day), one run over two half-days (Half-Day), a non-specific intervention control group, and a waiting list control group. Results indicate that the participants in the workshop groups improved more than those in either of the control groups, supporting the idea that the psychoeducational approach can be valuable and economical in a health promotion and public health context. The use of this format in clinical situations and in primary care settings is also discussed.