['Insulin resistance, decreased response of peripheral tissue to normal insulin levels, is known to be related to cardiometabolic diseases. Cardiopulmonary fitness is also considered to be related to these comorbidities. Therefore, we investigated the relationship between insulin resistance and cardiopulmonary fitness by performing a 3-minute step test in a Korean non-diabetes mellitus (DM) population.', 'A total of 118 non-DM subjects were enrolled during their routine health check-up. Insulin resistance was measured by calculating homeostatic model assessment-insulin resistance (HOMA-IR), and a 3-minute step test was performed to measure cardiopulmonary fitness.', 'Post-60 seconds exercise heart rate after 3-minute test (R60 heart rate) was correlated with age (r = -0.21, P = 0.02), education (r = 0.17, P = 0.04), body mass index (r = 0.23, P = 0.01), waist circumference (r = 0.28, P < 0.01), fasting insulin (r = 0.28, P < 0.01), HOMA-IR (r = 0.25, P < 0.01), low density lipoprotein-cholesterol (r = 0.28, P < 0.01), high sensitivity C-reactive protein levels (r = 0.22, P = 0.02), and baseline heart rate (r = 0.56, P < 0.01). In a step-wise multiple regression analysis, baseline heart rate (β = 0.79, P < 0.001), HOMA-IR (β = 0.65, P = 0.02), and systolic blood pressure (β = 0.15, P = 0.03) were identified as explanatory variables for R60 heart rates.'] Is cardiopulmonary fitness independently associated with insulin resistance in non-diabetes mellitus patients of a university hospital in Korea?