We used an infrared video camera and video tape recorder system to record and analyze nocturnal scratching in seven patients with atopic dermatitis (AD) and three non-itchy healthy controls. The patterns and the locations of scratching were successfully observed. Scratching bouts lasting more than 5 sec were counted, and the summation of the duration of all the scratching bouts (total scratching time, TST) was used as an index of nocturnal scratching. TST in patients with AD turned out to be some hundreds to ten thousands of seconds; the TST in controls was between zero and a hundred seconds. The infrared video camera system measured nocturnal scratching simply and reliably without disturbing the patients' sleep.