The use of cyclosporin A has been associated with several side-effects, inc
luding neurotoxicity. The mechanism of toxicity is not well known. We repor
t two patients treated with cyclosporin A who developed lesions in the cere
bral white matter associated with abnormally elevated cerebral blood flow v
elocities on transcranial doppler ultrasound and abnormal vascular appearan
ce on magnetic resonance angiography.