Dear Editor-in-Chief: Thanks to Dr. Fenske for his interest in our paper (1). In this paper, it was reported, that in highly trained swimmers, 24-h urinary cortisol/cortisone (C/Cn) ratio was moderately related to both training and performance, whereas Cn levels were only related to training. As indicated by Dr. Fenske, cortisol and cortisone excretions are subjected to circadian variations. In this respect, it was chosen to assess urinary free C, Cn, and C/Cn ratio from urinary volume collected over 24 h. Obviously, it was collected at various times, to avoid the circadian variations of urinary free C and Cn excretion (6). As indicated in the methods, urinary free C and Cn were reported to the total diuresis and creatinine excretion. Dr. Fenske suggested a reevaluation of the data taking into account the relation between 24-h urine volume and urinary C/Cn excretion. Reevaluating these data, no relationship was found between 24-h urine volume and urinary C/Cn excretion. Three main reasons explain this lack of relationship. Firstly, in Mericq and Cutler’s paper (5), it is only high fluid intake (5 L·d−1) that causes both increased diuresis (∼3.8 L·d−1) and urinary C output. By contrast, in the present study, the healthy subjects demonstrated daily urine outputs over the follow-up period (i.e., female: 804.4 mL·d−1; and male: 823.3 mL·d−1) and creatinine excretions (i.e., female: 1.0 g·d−1; and male: 1.2 g·d−1) within the physiological range, with no significant change over the three studied periods (data not shown). Secondly, it should also be emphasized, that in Mericq and Cutler’s paper (5), the authors write that “urinary free C was assessed using RIA [radio immunologic assay] which lacks absolute specificity for cortisol and thus yields values approximately twice as great as highly specific methods.” In the present study, a highly specific method (HPLC) was used. It allows the dissociation between C and its metabolites contrary to radio immunologic assays (7). Thirdly, in the literature, the data relative to the influence of water metabolism (i.e., water intake and urine output) on urinary free C are not consistent. In healthy subjects (5) and in one patient suffering from psychogenic polydispia (4), increased fluid intake, resulting in increased urine volume, have been shown to increase significantly urinary free C excretion. It is noteworthy that the increased urinary free C observed by Friedman et al. (4) was paralleled by increased urinary creatinine excretion that was not in line with Mericq et al. findings (5). Conversely, no significant correlation has been found between daily urine output, within the physiological range (i.e., 500–2500 mL per 24 h) and urinary free C in healthy women (8). Dr. Fenske himself reported conflicting reports concerning the influence of water diuresis on urinary free C (2,3). It is agreed that data concerning the influence of water metabolism on urinary free C excretion changes in healthy subjects as well as in trained subjects still need further investigation. However, taking into account the highly specific method used (HPLC), these doubts are not justified in the highly trained population studied with normal fluid intake. Djamila Atlaoui Laboratory of Physiology Jean Monnet University Saint-Etienne, France Jean-René Lacour Faculty of Medicine Lyon University Lyon, France Martine Duclos Laboratory of Neurogenetic and Stress University Bordeaux Bordeaux, France Jean-Claude Chatard Laboratory of Physiology Jean Monnet University Saint-Etienne, France