Algodystrophy is usually attributed to disorders of microcirculation, and one may reasonably expect to demonstrate these by the Doppler method applied to arteries. Ten patients with algodystrophy stage I were explored and compared with 10 healthy controls and 10 patients with diseases likely to encourage the development of algodystrophy. Systolic, diastolic and mean blood flow velocities were recorded at different levels in the limbs involved and compared with velocities recorded at the same levels in the limbs of healthy subjects and in the clinically healthy limb of control patients. Algodystrophic patients actually had local circulatory abnormalities consisting of an increase in mean velocity with a diastolic component. A diastolic velocity superior to 3 cm/sec on the main arterial axis of the affected limb, or a difference of more than 5 cm/sec in mean velocity between the right and left sides provided an early diagnosis of algodystrophy with an 80 p. 100 sensitivity in this small series. Moreover, in 3 out of 10 cases Doppler velocimetry demonstrated abnormalities at varying levels of the contralateral limb.