To confirm the reliability and validity of cardiovascular autonomic nervous system tests, RR-variation and Valsalva maneuver, coefficient of variation for triplicate tests was calculated. The testing data were collected from patients participating in the Statil Neuropathy Trial. Triplicate testing was done within a three-week period at three different time points: baseline, 12 months, and 18 months. BMDP Statistical Software was used in the analysis. There is no significant difference between the coefficients of variation between clinics for either RR-variation or Valsalva maneuver tests. The coefficient of variation of pooled data was not significantly different from the coefficient of variation of individual clinics. Furthermore, there was no evidence that there was a significant worsening of coefficient of variation with time. Thus, RR-variation and Valsalva maneuver provide reliable and reproducible results that do not vary in consistency over time.