Linear scleroderma is a rare, at times debilitating, disease with an unpredictable course. Currently, there is no satisfactory objective method for assessment of disease activity upon which to base therapeutic decisions. We evaluated 11 children with 18 linear scleroderma lesions (mean age 11.7 years, mean duration of disease 5.1 years) for disease severity and the presence of immunologic abnormalities, and attempted to correlate these results with thermography. Positive thermography was defined as warmer than surrounding skin or opposite limb by 0.5 degrees C. Six patients were thermography positive. Mean age, sex, disease duration and the presence of hypergammaglobulinemia and autoantibodies were similar in thermography positive and thermography negative patients. Six of 18 linear scleroderma lesions were thermography positive. All 3 new or expanding lesions were thermography positive. All 3 lesions that were resolving clinically were thermography negative. Three of 12 lesions that were clinically unchanged over a 6-month period were also thermography positive. In summary, thermography is a noninvasive test that appears to demonstrate active lesions in linear scleroderma. It is not influenced by previous soft tissue damage induced by linear scleroderma and may enable better monitoring of the effectiveness of proposed therapies.