Rates of nephrolithiasis are higher in males than females. The cause for this remains unclear, however animal models have demonstrated an association between sex steroid hormone levels and lithogenesis. This relationship in humans is less well established. This study from the urology team at the Mayo Clinic retrospectively reviewed the sex hormone levels: estradiol and testosterone, in 684 patients in an attempt to establish a relationship with nephrolithiasis. Six hundred and eighty-four men participating in the Olmstead County ‘natural history of prostatism’ study and who formed stones were included. This population had their sex hormones levels measured at the outset in 1990 and in the subsequent years. Median follow-up for stone formation was 12.8 years. On multivariate analysis, there was no significant association of serum hormones or percentage change of hormone levels with nephrolithiasis, although a trend toward higher baseline testosterone and stones was seen. The authors suggest that hormone manipulation to alter the risk of stone formation, namely men with stones and hypogonadism, should not avoid testosterone replacement simply because of their history of stones. This paper is steeped in limitations, especially related to the population group studied: Caucasian males, over the age of 40 years and no assessment of dihydrotestosterone and sex hormone binding globulin. Furthermore, there was no detail on stone type or urinary parameters. More work is required to explain the gender differences in nephrolithiasis.