To determine whether the complete correction of hyperglycemia of diabetes can rapidly improve abnormal peripheral nerve function, eight hyperglycemic insulin-requiring diabetics underwent 3 days of glucose control with an artificial endocrine pancreas, the BIOSTATOR Glucose Controller. Comparison of neurologic assessment before and after BIOSTATOR treatment showed improvement only in ulnar sensory conduction velocity (+ 3.2 +/- 1.4 meters per second, p less than 0.032) and no significant changes in 24 other nerve conduction measurements, computer-assisted examination, and scored neurologic assessment. Any significant beneficial effect on nerve function resulting from correction of hyperglycemia probably requires more than 3 days to be manifested.