In this prospective study computed tomography (CT) was used to monitor the response of compression therapy in 27 patients with chronic unilateral lymphoedema over a 12 week period. Computed tomography examination of abnormal and normal limbs (proximal and distal portions) was performed in the first, third and 12th weeks of treatment. Changes in cross-sectional area (CSA) and average densities of the different compartments within the proximal and distal portions of the abnormal limb were compared with the normal side. The most significant decrease in CSA occurred within the subcutaneous compartment of the distal portion (P = 0.002); the decrease in CSA of the proximal portion was also significant (P = 0.02) but changes in muscle and bone compartments were not significant. Significant differences in average density measurements of the subcutaneous and muscle compartments remained between normal and abnormal limbs following the conclusion of the study (P = 0.001 and P = 0.01, respectively). This study demonstrates that CT is a useful method for monitoring therapeutic response to compression therapy.