Concentrations of creatinine, uric acid and urea were measured in the blood and urine of female patients at the final stage of renal disease and on a regular lifelong programme of haemodialysis. The samples were collected in winter-time and in summertime. The same analytes were also measured in sweat fluid at the time of collecting summer samples. The results showed insignificant physiological seasonal changes for creatinine and uric acid and that the concentration of these compounds in the sweat fluid was low. Urea concentration in the sweat fluid was found to be present at a much higher concentration than the serum level (reaching in some cases 50 times the serum level). The possibility of using thermal induction as an alternative to haemodialysis is suggested. The presence of urea in the sweat fluid at such a high level suggests a selective transport mechanism across the eccrine sweat gland to clear the blood of a high urea level.