An 84-year-old woman presented with an acute onset of violent bilateral ballism-chorea. She was admitted to the local neurology unit, but not definite diagnosis could be made of the underlying condition, although she did appear to have bronchopneumonia. At autopsy the stomach wall was thickened, and the lesser curve lymph nodes were firm and enlarged. A single nodule was noted in the liver while the lungs appeared consolidated. Histology revealed a moderate-to-poorly differentiated gastric adenocarcinoma with extensive intravascular dissemination which included the central nervous system (CNS). Numerous small infarcts related to vessels occluded by tumour were present throughout the brain, and we feel that this was the underlying mechanism for the acute onset of ballism.