Mrs. H., aged 24 years, the mother of one child, pregnant for the fourth time, was a healthy Englishwoman. She was vaccinated on March 7, 1967, in the United Kingdom before emigrating to Australia. She was pregnant when vaccinated ; the last menstrual period had occurred on November 10, 1966, and the period of gestation was calculated as 15 weeks. Fcetal movements were noticed on March 17. The reaction was typical of a primary vaccination; she was not unduly ill, and she developed no complications. Five weeks later, during the journey to Australia, she developed intermittent vaginal bleeding and was con fined to her bunk aboard sh ip . On arrival in Sydney on April 19, she was admitted to hospital, where it was noted that the size of the uterus corresponded to a period of gestation of 23 to 24 weeks. At this stage, the period of amenorrhoea was 21 weeks. Fcetal movements were detected. Bleeding ceased, and she was discharged from hospital three days later. This was the last occasion on which fcetal movem ents were felt. A fortnight later, on May 4, the patient was readmitted to hospital in premature labour, and was delivered of a stf ll-born , macerated female fcetus. H er subsequent course was unev entful, and she was discharged from hospital on May 9.