Gonadotropin levels in isolated blood samples, integrated plasma concentrations (IC), and timed urinary collections have been compared in 5 males with delayed puberty and 7 normal adult males. There was a significant correlation between urinary levels in 24-h collection and those in each of four shorter timed collections for both LH and FSH. Similarly, 24-h integrated plasma concentration and 4-h (0800--1200 h) integrated plasma concentration obtained on 10 additional subjects showed significant correlation. The 4-h integrated plasma concentrations correlated with single blood samples or the mean of three samples obtained at 0800, 1200, and 1600 h. These 4-h plasma samples also correlated significantly with all urine collections for FSH but only with the 2200--0800 h urine collection for LH. The study suggests that LH and FSH levels in urine samples collected over several hours correlate with 24-h urinary excretion and that levels in single blood samples estimate the 24-h plasma integrated concentration.