Objectives: Quantify the effects of cold water immersion of the ankle on fractioned response time of the dominant lower limb. Design and Setting: A 2x2x5x5 crossover design with repeated measures on time and treatment directed data collection. The independent variables were gender, treatment, time (pretreatment, and post 15 seconds, 3 minutes 6 minutes and 9 minutes) and trial (5 trials for each time group). Response time (Tresp), reaction time (Treac), trial and surface temperature were measurement variables. Subjects: Thirty-six subjects, 18 females and 18 males were recruited from a physically active volunteer college student population. Measurements: Fractioned response time was tested following a 20 minute treatment. Response time and Treac were recorded by the reaction timer, and Tmov was calculated by taking the difference between Tresp and Treac. For each time/subject the high and low Tresp were discarded and the middle three trials were averaged and used for statistical analysis. A 2x2x5 ANOVA was used to determine overall differences between gender, treatment and time followed by Newman-Keuls multiple comparison tests. Results: Males were faster than females for Tresp, Treac and Tmov. Movement time and Tresp were slower with cold water immersion, but Treac was unaffected. Movement time and Tresp were fastest pretreatment, and slowest during the post 15-second time group. Though both Tmov and Tresp progressively sped up from the post 15-second through the post 9-minute time group, they did not return to pretreatment values when data collection discontinued. Conclusions: Immersing the dominant ankle in cold water for 20 minutes increases Tmov of the dominant lower limb; thereby increasing fractioned response time (Tresp).