The diagnosis and management of many soft-tissue lesions remains difficult largely as a result of a lack of objective assessment. It is considered that thermography may fulfil this role. During a therapeutic study of 56 tennis-elbow lesions, detailed clinical assessment was supplemented by serial thermography of the lateral elbow. A characteristic localized thermographic abnormality was found in 53 of the 56 affected elbows and only 3 of 60 (120 elbows) normal age-and sex-matched controls. Microcomputer analysis of the thermal gradient slope across the abnormal area showed a correlation with clinical state, reflecting recovery, and revealing a much smaller diurnal variation than was seen in the solely temperature-based parameters. Clinical features do show some variability both with regard to the site of tenderness and degree of involvement of supination and pronation. While these differences may have pathological significance they do not appear to have prognostic importance. Thermography is a useful objective method for assessment of tennis elbow and may aid the investigation and understanding of other soft-tissue lesions.