It is reported on a 27 year old female patient who was hospitalized twice during her first pregnancy (16th and 28th week) because of severe hyperemesis gravidarum. Severe clinical symptoms associated with severe alterations in the clinical chemistry posed a series of differential diagnoses. Several diseases as potential causes for unappeasable vomiting were taken into account. All traditional therapeutic efforts to relieve hyperemesis gravidarum including H2-blockers in high dosages were not successful. Treatment with omeprazole proved to be effective by stopping the vomiting immediately. After the delivery of a healthy child in the 37th week of pregnancy, several investigations were performed to exclude organic diseases. Etiology and symptoms of hyperemesis gravidarum are discussed with regard to the gastrointestinal tract and thyroid gland function.