The purpose of this study is to evaluate the effects of moisture vapor transport properties of four different groups of overgarments (OGs) on physiological, sensory, and comfort responses. These OGs were made from materials containing an impermeable film and three semi-permeable (or moisture vapor permeable) membranes with varying moisture vapor transmission rates (MVTR). The impermeable film had an MVTR of 5 g/m²/24 h, and the three moisture vapor membranes had MVTRs of 360, 670, and 864. These four OGs were evaluated under two environmental and work/rest conditions. The environmental conditions consisted of a warm environment, T_a = 29.2°C, 51 % relative humidity, V = 1.1 m/s and a cool environment, T_a = 18.4°C, 50 % relative humidity, V = 1.1 m/s. Eight men wore the OGs while performing 4 h of intermittent exercise. Rectal temperature, an 8-point mean weighted skin temperature and heart rate were continuously recorded. Skin wettedness was calculated from dew point sensors under the OG. Mean body weight loss and moisture absorption by the OG, underwear, and foot-wear were measured from pre- and post-experiment weights. A sensory and comfort rating questionnaire was presented to the volunteers every 30 min. During prolonged intermittent exercise in moderate environmental conditions, volunteers wearing OGs with MVTR of 670 and greater produced less thermo-physiological stress, independent of changes in perceived comfort. Perceived comfort of the MVTR 5 OG was significantly lower than all other garments at 18.4°C. At 29.2°C, both the MVTR 5 and 360 OG produced lower comfort, but not significantly. At 29.2°C, volunteers were significantly warmer, sweatier, and experienced significantly greater moisture on their skin, undergarments, and inside their OGs than at 18.4°C, and these sensations increased over time. However, at 29.2°C, perceived comfort differences among MVTR levels were either not significant or not associated with MVTR level.