Abstract: A hand-held device which measures the period of a heartbeat, converts the measured period to beats per minute and displays the result on a digital read-out indicator. In using the device, the subject places his thumb in a depression formed in its case. Located in the depression are a light, a photo-sensor and an activating switch. The sensor responds to light transmitted through the thumb, the transmitted light being pulsed as blood is pumped into the thumb by the action of the heart.