The time of sit-stand and stand-sit transition and its duration were measured using a miniature gyroscope on the chest and a portable recorder on the waist Based on a simple model and wavelet analysis, three parameters related to postural transition, namely the average and standard deviation of transition duration and the occurrence of abnormal successive transition, were provided for evaluating the falling risk. The comparison between two groups of elderly subjects (i.e. fallers and non-fallers) shows that these parameters were significantly correlated to failing risk (p<0.02). The integration of the sensor and the recorder in a same module allows providing a system especially adapted for ambulatory instrumentation and tele- alarm systems.