Abstract  An original method for assessing the human functional state (FS) is described. The method is based on stabilography in a sitting position. Changes in the position of the total center of pressure on a stabilographic support were monitored in 32 healthy subjects who were in an arbitrary sitting position, in the state of quiet wakefulness with the eyes open or closed. The obtained data were analyzed in terms of the theory of complex systems. The recorded signal was considered as an output of a complex, half-open biomechanical system responding to numerous external and internal stimuli. The necessary and sufficient set of parameters for qualifying the FS has been determined, and the ranges of normal values of these parameters have been estimated. The sensitivity of the method to changes in the FS and the individual stability of some calculated kinetographic parameters have been demonstrated. The method is applicable to studies in psychotherapy, perception psychology, operator performance, and neurological rehabilitation science.