A method of monitoring the autonomic nervous system of a subject, wherein the method comprises the following steps: • the acquisition of at least one physiological signal, which comprises W heartbeats, each heartbeat being detected at an instant t, with t lying between t x-w+1 and t x, the instant t x being the last heartbeat of the W heartbeats; • the generation of a data item which depends on the variability of the heart rate with respect to all the W heartbeats, with VFC comprising W-1 RR intervals separating two consecutive heartbeats detected at the instants t k-1 and t k respectively and each RR interval having a duration of a k = t k - t k-1 where k = (X-W+2)... X; characterized in that it consists in: • calculation of the following parameters using at least one microprocessor: - the parameter TAS(t x), representing the level of activity of the sympathetic system and which depends on the ratio on the one hand between a first sum obtained by summing, among the a k values, only those which are greater than the value a k-1 of the immediately preceding interval and a second sum obtained by summing all the W-1 values a k; and on the other - the parameter TAP(t x) representing the activity level of the parasympathetic system which depends on the ratio between, on the one hand, a first sum obtained by summing, among the a k values, only those which are less than the value a k-1 of the immediately preceding interval and a second sum obtained by summing all the W-1 values a k; and on the other hand - the parameter NS(t x) representing a stress level of subject at instant t x and calculated by applying the following equation: NS t X = 100 + TAS t X − TAP t X providing data representative of the said at least one parameter. • the acquisition of at least one physiological signal, which comprises W heartbeats, each heartbeat being detected at an instant t, with t lying between t x-w+1 and t x, the instant t x being the last heartbeat of the W heartbeats; • the generation of a data item which depends on the variability of the heart rate with respect to all the W heartbeats, with VFC comprising W-1 RR intervals separating two consecutive heartbeats detected at the instants t k-1 and t k respectively and each RR interval having a duration of a k = t k - t k-1 where k = (X-W+2)... X; characterized in that it consists in: • calculation of the following parameters using at least one microprocessor: - the parameter TAS(t x), representing the level of activity of the sympathetic system and which depends on the ratio on the one hand between a first sum obtained by summing, among the a k values, only those which are greater than the value a k-1 of the immediately preceding interval and a second sum obtained by summing all the W-1 values a k; and on the other - the parameter TAP(t x) representing the activity level of the parasympathetic system which depends on the ratio between, on the one hand, a first sum obtained by summing, among the a k values, only those which are less than the value a k-1 of the immediately preceding interval and a second sum obtained by summing all the W-1 values a k; and on the other hand - the parameter NS(t x) representing a stress level of subject at instant t x and calculated by applying the following equation: NS t X = 100 + TAS t X − TAP t X providing data representative of the said at least one parameter. - the parameter TAS(t x), representing the level of activity of the sympathetic system and which depends on the ratio on the one hand between a first sum obtained by summing, among the a k values, only those which are greater than the value a k-1 of the immediately preceding interval and a second sum obtained by summing all the W-1 values a k; and on the other - the parameter TAP(t x) representing the activity level of the parasympathetic system which depends on the ratio between, on the one hand, a first sum obtained by summing, among the a k values, only those which are less than the value a k-1 of the immediately preceding interval and a second sum obtained by summing all the W-1 values a k; and on the other hand - the parameter NS(t x) representing a stress level of subject at instant t x and calculated by applying the following equation: NS t X = 100 + TAS t X − TAP t X providing data representative of the said at least one parameter.