This randomized, controlled trial tested the hypothesis that women identified as more vulnerable to developing postnatal depression who attended two specific antenatal groups and one postnatal group have a reduced frequency of postnatal depression from 37 to 15 percent at 6 weeks, 12 weeks, and 6 months postpartum. A modified antenatal screening questionnaire was completed, and women identified as more vulnerable to postnatal depression were stratified by parity and randomly allocated to receive extra support groups or to a control group. The Edinburgh Postnatal Depression Scale (EPDS) was used to detect postnatal depression. Attendance at the support groups was low, 31 percent overall. At six weeks, in the intervention group, 8 (13%) of 64 women scored high (> 12) on the EPDS, compared with 11 (17%) controls. Similarly, at 12 weeks 7 (11%) of 63 versus 10 (15%) of 65 women scored higher than 12, and at 6 months, 9 (15%) of 60 versus 6 (10%) of 64 women scored higher than 12, indicating that the intervention did not reduce postnatal depression. It is possible that the method of applying the intervention, using groups separate from the standard antenatal classes, may have affected attendance. More research is required into ways of reaching and supporting women who may become depressed.