In a review of 90 twin pregnancies monitored by antenatal cardiotocography there were 8 cases of subsequently proven fetofetal transfusion syndrome. In 2 of these evidence of severe fetal stress had indicated immediate delivery; the 4 babies survived in circumstances that were perilous. In 1 case there was no evidence of critical fetal reserve but the recipient twin died, this probably representing an acute fetofetal transfusion during labour. In the 5 milder cases with no evidence of stress on cardiotocography, all babies survived and they required minimal or no treatment for problems relating to the fetofetal transfusion. In multiple pregnancy the cardiotocograph offers the additional bonus of detection of fetal compromise due to fetofetal transfusion.