African Americans are more insulin resistant than Caucasians. A single bout of moderate-intensity exercise reduces insulin resistance in sedentary Caucasian individuals. The impact of a single bout of exercise on insulin resistance has never been studied in African Americans. The purpose of this experiment was to evaluate the impact of a single bout of exercise on insulin resistance in African-American women. DESIGN: Insulin resistance was assessed in 10 sedentary, over-weight or obese African-American women during a sedentary and exercise condition over a two-day period. During the sedentary condition, participants fasted overnight and sat quietly in the laboratory for 75 minutes. During the exercise condition, participants completed 75 minutes of brisk walking on a treadmill. Ninety minutes following each condition, participants completed an oral glucose tolerance test (OGTT). Three-and-a-half hours later, subjects consumed a standardized meal [meal tolerance test (MTT)]. RESULTS: The insulin response to the OGTT was 18% lower (p=0.046), and insulin sensitivity was 18% higher (p=0.042) in the exercise condition compared to the sedentary condition. There were no differences between conditions following the MTT. CONCLUSIONS: These results indicate that overweight/obese, sedentary, insulin resistant African-American women had a significant improvement in insulin sensitivity from 75 minutes of brisk walking.