A prospective study was designed to test the efficacy of pressure at the P6 (Neiguan) acupuncture point, in preventing morning sickness. Three groups of patients in early pregnancy recorded the severity and frequency of sickness over a period of 4 consecutive days following daily pressure at P6 point, pressure at a point near the right elbow and with no treatment. Troublesome sickness was significantly less in both the genuine (23/119) and dummy (41/112) pressure groups as compared with the control series (67/119). When the data are adversely 'weighted' to compensate for the lower incidence of fully completed returns in the active treatment groups, only the P6 group show a significant reduction in sickness. No side effects occurred in either group and while anticipation of benefit may offer a partial explanation for the findings, pressure at the Neiguan point appears to have a specific therapeutic effect.