In this paper by Morag A Taylor and colleagues (19-26 August, pp 471-6) an inadvertent mix up over colours in one of the figures may have led to some confusion in interpreting the results. In the right hand column of figure 3 (p 474) the three pairs of points should not be black as shown: instead, the upper point in each pair should be blue (placebo) and the lower point white (homoeopathy).