The authors studied the psychological variables of 25 men who participated in the winter-over team of an Indian expedition to Antarctica for possible associations with seasonality and isolation. It was found that increased cigarette smoking was associated with the stress of the beginning of isolation (March), sleep difficulty was associated with midwinter (June), rapport was at a minimum at the point of maximum isolation in temporal terms (September), and decreased satisfaction with work and life situations was associated with continued isolation (December, January). The study suggested that variables postulated to affect performance undergo changes during the course of wintering over in Antarctica.