The present study investigated the effects of individual differences along the dimension of dispositional optimism-pessimism on comparative risk perception in relation to the prospect of developing AIDS. 104 university students completed the Life Orientation Test of Scheier and Carver and estimated the likelihood of AIDS happening to themselves and the average university student. A split at the median on the Life Orientation Test divided subjects into optimists and pessimists. Dispositional optimists and pessimists rated their own likelihood of developing AIDS as less than that of the average student. Moreover, subjects classified as optimistic and pessismistic did not differ significantly in their ratings of comparative risk perception.