The effects of academic examination stress on health behavior was assessed in university students. It was hypothesized that the anticipation of examinations would lead to increases in cigarette smoking and alcohol consumption, and to decreases in physical activity, and that effects would be particularly salient in students with low social supports. One hundred eighty students were divided into exam-stress (51 women, 64 men) and control (49 women, 16 men) groups, and were assessed at baseline and then within 2 weeks of exams, or an equivalent point for the control group. Perceived stress, emotional well-being and health behaviors were assessed by questionnaire and interview. The exam-stress group reported significant increases in perceived stress and emotional distress between baseline and exam sessions, but responses were not affected by social support availability. The controls showed no systematic changes in health behaviors. In the exam-stress group, smoking increased by an average of 54.7% between sessions in women with few social supports, but remained stable in men. There was a decrease in alcohol consumption of 17.5% in students with high social support between sessions, while those with low social supports showed an average increase of 18.5%. Physical activity decreased between baseline and exam sessions in the exam-stress group, but was not affected by social support. The results are discussed in relation to the effects of naturally occurring episodic stress on health behaviors, and the role of social support in moderating responses.