The classical Stroop color-naming task was converted to a Web administered version and tested against a conventional computerized version. In the first experiment, 20 male and 20 female participants were tested individually on both Stroop versions in random order. Both versions resulted in strong Stroop effects, but response times were slower overall for the Web-Stroop. A second experiment with 28 participants showed that the test results on the Web-Stroop could be replicated in a less controlled experimental setting, for example in the participant’s own home. In conclusion, findings suggest that administration of the Stroop color-naming test, and response time measurement in milliseconds on a personal computer, is possible via the Internet.