The Stoplight Task, a procedure involving a computer analog of a stoplight, was evaluated for assessing risk taking in humans. Seventeen participants earned points later exchangeable for money by completing a response requirement before the red light appeared on a simulated traffic light. The green light signaled to start responding; it changed to yellow at different points into the response requirement. The yellow light, which varied unpredictably in duration, was eventually replaced with a red light. Participants could stop or continue responding when the yellow light appeared. Stopping protected earnings; completing the response requirement before the red light earned money; continuing but failing to complete the response requirement before the red light appeared could result in money loss with 12.5% or 100% probability. The probability of risk taking (running the yellow) was lower when the probability of monetary loss was 100% and when the yellow light appeared early in the completion of the response requirement. Participants scoring higher on risk-taking and impulsivity personality rating scales behaved "riskier" in the stoplight task. Potential applications of the Stoplight Task are suggested. (Contains 2 tables and 3 figures.)