Accurate classification of diabetic foot ulcers is essential for inter-clinician communication, assessment of healing tendency and determination of treatment options. The aim of this study was to assess the inter-observer agreement (IOA) of the most commonly used classification systems for diabetic foot ulcers; the Meggitt-Wagner (MW) and the University of Texas (UT) systems. In this study, 95 clinicians judged digital photographs of diabetic foot ulcers in various stages of healing. Wound depth was classified along the grades of the MW and the UT systems. IOA of the MW and UT systems was only moderate among the clinicians. This moderate agreement demonstrates that the MW and the UT systems appear not to be useful as single instrument and should always be used in combination with additional clinical information to avoid erroneous interpretations.