The conductivity of subcutaneous tissue was measured in rats with various types of experimental oedema. The measured values depended on the water content in tissues and not on the origin of oedema. The conductivity measurements of the subcutaneous tissue above the ankles were also used in patients with several types of clinical oedema in comparison with a group of normal subjects. The method is simple and well reproducible. It is suitable particularly for the evaluation of changes in oedema development.