Changes in skin temperature cause great changes in blood flow and capillary blood pressure. The new technique presented here makes it possible to control the temperature of the finger during nailfold capillaroscopy. Automatic temperature control, both for warming and cooling, is made possible with the aid of a temperature-controlled finger holder. The temperature of the finger holder can be automatically matched to the spontaneous skin temperature of the examined finger, or the finger holder temperature and temperature change velocity can be set digitally to a desired value. We used this new technique in a local cold stress test on 9 healthy controls (3 men, 6 women) and 9 patients (3 men, 6 women) with Raynaud's phenomenon due to systemic sclerosis. We simultaneously measured capillary red blood cell velocity (CBV) and laser Doppler flux (LDF) in adjacent areas of the finger nailfold with three different cooling procedures (8, 10, 12 degrees C for 5 min). CBV and LDF values showed the most pronounced differences between patients and controls at 12 degrees C. This new technique supplements capillaroscopy with full temperature control and defined temperature changes. It can also be combined with measurements of LDF and capillary blood pressure. In view of the disadvantages of other cooling methods we recommend this new and easy-to-handle technique for clinical practice and research.