Intra-individual variability for serum and urinary hormones has been inadequately considered in previous studies. Therefore, in the planning phase of a prospective study of Hormones and Diet in the Etiology of Breast Cancer (ORDET study), androgen levels have been examined at two different times in 56 women (26 in premenopause and 30 in postmenopause). Hormonal measurements in serum showed a good level of agreement for both premenopause (pre) and postmenopause (post): androstenedione pre r = 0.70 (p less than 0.0001), post r = 0.77 (p less than 0.0001); testosterone pre r = 0.73 (p less than 0.0001), post log values r = 0.74 (p less than 0.0001). Dihydrotestosterone showed a good level for premenopause only: log values pre r = 0.82 (p less than 0.0001), post r = 0.41 (p less than 0.05). Agreement levels in urine were inferior to those of serum: testosterone pre r = 0.53 (p less than 0.05), post r = 0.41 (p less than 0.05); androstanediol log values r = 0.46 (p less than 0.001), post log values r = 0.57 (p less than 0.05). Correlation between the two measurements improves considering age, parity, time of blood collection and, for urine, the interval of sample collections.