The aim of this study was to describe the epidemiology of chronic wounds in a large cohort of patients from a tertiary hospital out-patient clinic, and examine the significance of serum mannan-binding lectin for the occurrence and clinical presentation of such wounds. The study comprised 489 consecutive patients with chronic foot and leg ulcers. A clinical classification of wound- aetiology was performed, and mannan-binding lectin was measured in the sera of patients and healthy controls. The patients presented with 639 wounds altogether; diabetic foot ulcers (309), venous leg ulcers (188), arterial ulcers (109), and vasculitis (33). The mannan-binding lectin levels of patients with venous leg ulcer, alone or in combination with other types of wounds, differed significantly from the control group, and the frequency of values < 100 ng/ml was significantly higher. In diabetic and arterial ulcer patients the frequency of values >or= 3000 ng/ml was significantly higher than that of the control group. This suggests a role for the innate immunity in the pathology of venous leg ulcers, and indicates different roles for mannan-binding lectin in the development of ulcers with different aetiologies; it further suggests that mannan-binding lectin substitution should be tested in a controlled clinical trial.