Abstract This paper investigates the effect of risk aversion on an individual's probability of being self-employed by using psychometric data from a large, population-based cohort of Finns born in 1966. We found that our measure of risk aversion, a facet of a basic temperament dimension, harm avoidance, has a significant negative effect on self-employment status. Since this measure is directly derived from a highly valid biosocial theory of normal personality variation (Arch. Gen. Psychiatry 44 (1987) 573) whose scalable dimensions manifest well before adulthood and remain stabile over lifetime, we argue that risk aversion is a psychological factor causative of the choice to become self-employed. ©2004 Elsevier B.V. All rights reserved.