For ethical reasons waiting list controls have been preferred to no treatment controls, provided the wait is still shorter than that for routine services. However, could significant differences arise from the wait being detrimental rather than the intervention being beneficial? Despite the number of studies employing this design, few have analysed intervention trials from the perspective of the waiting list controls rather than the experimental group. A Full Day Stress Management Workshop programme which had run successfully in Birmingham, was repeated in three areas in the South East of England. The data from the four areas were reanalysed to assess progress within the control group and to compare the final assessment points for the two groups. The control group did not show any significant deterioration during the three month wait for their workshop. Three months after their respective workshops, scores in the control groups did not differ significantly from those of the experimental group.