From the skin surface of patients, suffering from different skin diseases, (crude) sweat was obtained by thermal stimulation: Specific gravity, pH, Na, K, Ca, Cl, free and esterified phosphate, urea and ammonia were determined. Significant positive correlations appeared between specific gravity and Na or K, between H and K, Ca, urea or ammonia, between Na and K or Cl, between K and Ca or free phosphate, between Ca and ammonia and between urea and ammonia. Significant negative correlations appeared between H and Na or Cl, between Ca and Cl, between free phosphate and ammonia and between esterified phosphate and urea. The Ca and H concentrations, in addition to the Na, K and Cl concentrations, behaved as random samples from a normally distributed population. The Na/K ratio for subjects over 50 appeared to be raised; the Na/K and Cl/K ratios in psoriasis and atopic dermatitis were lowered and in chromium dermatitis raised.