The relation between water loading and electrolyte excretion in dogs fed on a meat diet proved impossible to evaluate owing to the large variability in electrolyte excretion rates in control experiments.2. In animals fed a synthetic diet of constant and known composition the administration of a water load of 2.5% of body weight caused significant increases in the rate of excretion of sodium (P < 0.01) and potassium (P < 0.05). The chloride excretion rate also increased in the one animal tested.3. The significance of these results is discussed.