The effects of arsenic (7440382) on nerve conduction velocities were studied in Alaskan residents with naturally contaminated drinking water. Subjects were 147 residents of Ester Dome, Alaska, aged 17 to 57, with an average length of residence of 74 months. Drinking water and urine samples were analyzed for arsenic content. Subjects were examined for neuropathy, and nerve conduction was measured at the peroneal motor nerve, sural sensory nerve, and ulnar sensory and motor nerves. Well water arsenic concentrations ranged from 1 to 4781 micrograms per liter, with a mean of 347.3 and a median of 41. Urinary arsenic concentrations ranged from 6 to 4964 micrograms per liter with a median of 50.9. Six subjects had symptoms or physiologic findings compatible with mild sensory peripheral neuropathy. One or more nerve conduction velocities were abnormal in 13 subjects, but nerve velocity measurements were not related to estimated daily arsenic ingestion or arsenic concentrations in water or urine. Only one subject, a diabetic, had both abnormal nerve velocities and signs of neuropathy. The authors conclude that nerve conduction velocities are insensitive in screening for subclinical neuropathy in subjects exposed to inorganic arsenic.