A series of 868 women in the last 4 weeks of pregnancy were examined for the presence of T. vaginalis by direct microscopy of freshly prepared wet films and by three culture methods; 32 (3-7 per cent.) were found to give positive results. Fourteen of the mothers with trichomoniasis at confinement had female babies, and these, together with a matching fourteen controls, were examined on three occasions by identical methods and within 21 days of birth. No baby gave positive results. On statistical examination it is very unlikely that with a much larger sample the number of positive findings could have been greater than 23 per cent. This is at variance with recent Polish work. These results suggest that neonatal infection in female babies, although a recognized clinical entity, is rare and unlikely to make any substantial contribution to the high incidence of trichomoniasis in women.