This study evaluated the influence of simple motor response time on the risk of falling among 202 stroke patients admitted to a rehabilitation hospital. All patients were tested within 2 weeks of admission to hospital on a computerized response time task. Visual stimuli were presented centrally, in the left and in the right visual fields. Three response times were calculated for each patient. Using the response time from the most impaired field, the 95 fallers generally had slower response times than did the 107 non-fallers (on average, 2.50 s vs. 1.93 s). However, response time was only significantly slower when the visual stimuli were presented in the left visual field (on average, 1.99 s vs. 1.39 s). As response time increased so did the risk of falling, demonstrating a dose-response effect. In comparison to patients with 'normal' response times (0.0-0.50 s), patients with response times between 2.00 s and 2.50 s had a sevenfold increase in the risk of falling. Previous research has shown that the response time of stroke patients improves over time, indicating that response time may be one factor influencing falls which is indeed modifiable. A suggestion is made to include the assessment of response time as a screening tool for identifying persons at elevated risk to fall as it is easily and accurately measured and as interventions aimed at improving response time are available.