A method of studying edema using magnetic resonance imaging (MRI) is presented. Three patients with lower extremity edema due to congestive heart failure were imaged with a 0.6 tesla system before and after diuresis. Edge detection algorithms were utilized to precisely outline regions of interest for quantification. Water and nonwater elements were separated within the region of interest to quantify water content. The results show that: (1) Edema can be quantified by use of MRI. (2) Subcutaneous edema is distributed along defined planes (ie, nonuniformly). (3) Increased water content is present not only in the subcutaneous tissue but also in deeper lying muscle.