BACKGROUND The aim was to examine cadexomer iodine paste in a comparative clinical trial. METHODS A 12-week, randomized, open, controlled, multicenter, multinational trial in patients with exudating, venous leg ulcers of cadexomer iodine paste (Iodosorb/Iodoflex), hydrocolloid dressing (Duoderm E, Granuflex E), or paraffin gauze dressing (Jelonet) was carried out. All patients used short-stretch compression bandages (Comprilan) throughout the study. The primary efficacy variable was a reduction in ulcer size (%), and the secondary end-point was the time taken to stop exudation, when the patient had completed the study according to the protocol. A total of 153 patients entered the study and were treated for 12 weeks or until cessation of exudation. RESULTS The mean reduction in ulcer size in all patients was 62% with cadexomer iodine vs. 41% and 24% for hydrocolloid and paraffin gauze (ns). Of those treated for 12 weeks (n = 51), ulcer area reduction was 66% for cadexomer iodine and 18% for hydrocolloid (p = 0.0127). For the whole material, the rate of healing (ulcer area reduction per week) was significantly higher for cadexomer iodine than for paraffin gauze (0.64 cm2/week vs. 0.19 cm2/week, p = 0.0353). The treatment costs were similar in all groups; however, when the costs were correlated with healing over a 12-week period, cadexomer iodine paste was found to be more cost effective than hydrocolloid dressing or paraffin gauze dressing. CONCLUSIONS This study shows that cadexomer iodine paste is an efficient, cost-effective and safe alternative to hydrocolloid dressing and paraffin gauze dressing for the treatment of venous leg ulcers.