Experiments were carried out to clarify the effects of wearing three different types of plastic ankle-foot orthosis (AFO) (A : traditional plastic AFO, B : A＋marketed hygroscopic liners, C : A＋vent holes with hygroscopic liner formed to fit the AFO) on oral temperature, temperature and humidity inside clothing (at sole, calf and chest), and thermal and wetness sensations on four students (age : 20 to 21, height : 150 to 172cm, weight : 44 to 94kg) during rest and while walking in the experiment room (30℃). The temperature and humidity inside clothing (at sole and calf) and thermal and wetness sensations increased when a plastic AFO was worn. The increase in the thermal and wetness sensations when wearing a plastic AFO tended to be highest for Type A and lowest for Type C under these experimental conditions. It is suggested that the humidity inside clothing had some influence on the sensation of wetness. Further study is needed on improving the comfort of plastic AFO with no hygroscopicity or water absorbency when worn tightly.