Two men, aged 63 and 71 years, developed a gross action tremor and dysesthesias several months after an intracerebral hemorrhage. CT and MRI showed a small hemorrhage in the posterior region of the lateral nucleus of the thalamus in each patient. The tremor occurred on movement, had frequencies of 2.5-4.5 Hz and the amplitude varied depending on the joint position of the limb. Ceruletide (a cholecystokinin analog) 0.8 micrograms/kg i.m. produced a marked reduction in the action tremor and improved motor function. This effect appeared 10-15 min after the injection, and lasted for up to 4 weeks. It is suggested that ceruletide may be of value in the treatment of action tremors following a thalamic lesion.