Thyrotoxicosis has a variety of presentations. Vomiting as a main presenting symptom of thyrotoxicosis is uncommon. We report a 40-year-old male with thyrotoxicosis who presented with sustained vomiting as the main symptom. He also had weight loss, about 10 kg over this 20-day period, and dizziness, particularly in the upright position. Esophagogastroduodenoscopy and abdominal ultrasonography were negative. Laboratory data were unremarkable except serum T4 of 21.2 microg/dl, T3 of 574 ng/dl and TSH < 0.03 microIU/ml. The patient's serum microsomal antibody was positive at a titer of 1:409,600, but serum thyroglogulin antibody was negative at a titer of less than 1:100. The symptoms improved after adminstroction of propylthyrouracil and propranol. A total of 31 such cases have been reported in English literature. The mean age of the patients was 46 +/- 14 year with a range of 19 to 68 years. Only 4 patients, including ours, were male. Weight loss was found in about half of them and might be an important clue. Thyrotoxicosis should be considered in differential diagnosis of unexplained vomiting.