Abstract Risk taking is predicted to vary with future discounting, as immediate rewards would be overvalued compared to those in the distant future. Degree of future discounting may be increased by unpredictability in the childhood environment. Here we assess relationships among risk taking, future discounting, the developmental environment, and biological factors, using surveys of 151 college students (19.2% men and 80.8% women; mean age 22.9). In structural equation models, environmental unpredictability had both direct and indirect effects on risk taking. Much but not all of its effect was mediated by future discounting.