A study of the sural nerve was undertaken to determine latency to onset and peak, duration of action potential, amplitude, and conduction velocity in 33 children, 1 to 7 years old. Multiple tests per patient resulted in 140 measurements per variable. To determine if the interpatient measurement variation was a significant factor compared to the intrapatient differences, one-way analysis of variance was performed. With each variable the F statistic showed the interpatient variation was significantly different (P less than .001) than the intrapatient measurement variation. There was no significant age effect in the latency to onset and peak, the amplitude, and the duration of action potential. The mean value for latency to onset was 2.430 msec, latency to peak 2.997 msec, duration 2.161 msec, and amplitude 8.736 muV. Age was highly significant (P less than .001) with conduction velocities calculated using latency to onset (CV1) and latency to peak (CV2), since distance was less in the younger child, according to the formulas: CV1 = 47.29 + 1.96 (age in years) and CV2 = 38.56 + 1.50 (age in years). Using regression analysis, temperature had no significant effect on CV1 or CV2.