Objective and methods: To investigate from the HERITAGE Family Study database, 13 steroid hormones (androstane-3α, 17β-diol glucuronide, androsterone glucuronide, cortisol, dehydroepiandrosterone (DHEA), DHEA ester (DHEAE), DHEA sulfate (DHEAS), dihydrotestosterone (DHT), estradiol, 17-hydroxyprogesterone, progesterone, pregnenolone ester, sex hormone binding globulin (SHBG) and testosterone in each sex for their relationships with age, body mass index (BMI), race and key lifestyle variables. Sample sizes varied from 676 to 750 per hormone. Incremental regression methods were used to examine the contributions of the variables to steroid hormone variability. Results: Age was a major predictor for most steroid hormones. The greatest contribution of age was a negative relationship with DHEAS (R2 = 0.39). BMI was also associated with the variability of several steroid hormones, being the most important predictor of SHBG (R2 = 0.20) and of testosterone (R2 = 0.12) concentrations. When age and BMI were included, race still contributed significantly to the variations in cortisol (R2 = 0.02 for men and 0.04 for women), DHT (R2 = 0.02 for men and 0.03 for women), and progesterone (R2 = 0.03 for women). Nevertheless, race appeared to be less important than age and BMI. In addition, lifestyle indicators (food and nutrient intakes, smoking and physical activity) influenced steroid hormone variability. Their contributions, however, were minor in most cases once age, BMI and race had been taken into account. Conclusions: We conclude that age was the most important factor, followed by BMI, race and lifestyle factors in explaining steroid hormone variability.