Proceeding from a formal definition of heart rate variability, some mathematical and statistical techniques from sampling statistics and time series analysis for the analytical evaluation of heart rate variability for ergonomics purposes are presented and compared. The concept of sampling statistics gives a measure of heart rate variability, arrived at by combining two measures, which were chosen according to a definite criterion. The applicability of this measure is discussed; especially with respect to serial correlation influences when using statistical tests. The two main methods of spectral analysis—the calculation of the transformed autocovariance function and of harmonic analysis–are presented. The influences of interpolations, algorithms and physiological effects are discussed. A possible measure of heart rate variability, calculated by spectral estimates, is proposed and some results are given.