In this paper, a digital optoelectronic step counter developed for monitoring the movements of a postsurgery patient is introduced. After all orthopaedic or a cardiovascular surgery, patient movements must be restricted; yet, a certain amount of daily activity is necessary as determined by the doctor. The amount of this activity can be quantitatively determined by counting the number of steps of the patient. The step counter developed for this purpose uses a high performance monochromatic phototransinitter and a high sensitive photodetector and it is placed on the patient's shoes. When step counts reach a preprogrammed (weekly or daily) set value, the patient is warned to stop further activity by an audio or visual warning.