Objectives: Determine if numbness differs in magnitude and duration between 10-, 15-, and 20-min ice bath immersions, when temperature was held constant. Design: Dependant variables; sensation of pressure (g), perceived pain (cm), and skin temperature (º C). A repeated measures 3 X 19 factorial guided this study. Conditions were 10-, 15-, and 20-min ice bath immersions. Measurement times were before immersion, 1, 3, 5, 7, 9, 10, 11, 13, 15, 17, 19, and 20 min immersion, and 1.5, 3, 5, 7, 9 and 11 min postimmersion. Subjects: Eighteen college-aged volunteers. Measurements: Subjects participated in three ice bath immersions (10, 15, and 20 min). Sensation of pressure was tested over the anterior talofibular ligament prior to immersion, and 1.5, 3, 5, 7, 9, and 11 min postimmersion. Cold induced pain was recorded at baseline (prior to treatment), every 2 min during immersion (beginning with 1 min), immediately following foot removal (10, 15, and 20 min), and directly following each monofilament reading (1.5, 3, 5, 7, 9, and 11 min posttreatment). Water bath and skin temperature were recorded every min (baseline to 11 min postimmersion). ANOVA's and Tukey-Kramer multiple range tests were used to determine significance. Results: Water bath temperature was held constant at 1º C. Loss of sensation was greater following 20 min of immersion than 10 min of immersion at all postimmersion measurement times. The greatest loss of sensation was at 1.5 min following the 20-min immersion. Cold induced pain was greatest, in all conditions, during the first 5 min of immersion. Pain peaked at 1 min of immersion and declined sharply until 9 min after immersion. Postimmersion pain was significantly greater following 20 min of immersion than 10 or 15 min of immersion. Skin temperature did not differ among conditions at baseline or during immersion. Conclusions: Our research supports clinical recommendations of 12-20 min initial immersion during cryokinetics. There was no difference in water or skin temperature between groups; therefore, the increased magnitude and duration of numbness following 20-min immersion was due to the increased length of immersion. Prolonging immersion past the point of perceived numbness may be beneficial.