Gross fetal movement was detected using a lower frequency ultrasonic Doppler shift than that used in the study of fetal heart action. The movement signal was changed into deflection which was recorded on CTG chart simultaneously with the fetal heart rate (FHR), and was called the fetal actocardiogram. Visual analysis of the actocardiogram showed bursts of active fetal movements in the active fetal state which were concordant with acceleration of FHR. The analysis was useful in the study of fetal behavioural states. Imminent fetal distress produced a loss of FHR acceleration which was accompanied by a burst of fetal movement, i.e. a true non-reactive state of the FHR. The output of the actocardiograph was analysed using a PC98XA computer with a simple statistics of deflection amplitude and interval, displayed as 3-dimensional histograms of the number and frequency, and the formation of the envelope curve of the deflections. The study demonstrated that it is possible to recognize fetal behavioural states automatically. This includes active and resting fetal states as well as fetal breathing movements.