Visual evoked potentials (VEPs) to repetitive flash stimuli were abnormal in 10 patients with documented hydrocephalus. Abnormalities included latency delays, fatigability, and asymmetries. Both latency and wave form disturbances improved in the postshunt period. Clinical progression of the hydrocephalus occurred in several patients, and this correlated well with worsening of the VEPs. We suggest that this noninvasive technique may be valuable in following patients with cerebrospinal fluid shunts, patients with presumed “arrested” hydrocephalus, and patients who are being weaned from their shunts.