1. The effect of a rapid local reduction in finger temperature on finger nailfold capillary blood pressure and blood cell velocity was investigated in healthy subjects. 2. Cooling was achieved by placing the finger into an adjustable copper cylindrical finger holder, which incorporated a Peltier element within its base; thus the entire finger from just distal to the nailfold to the interphalangeal joint was cooled. The Peltier element was cooled to 8 degrees C for 5 min. 3. Finger tip temperature was reduced to 76 +/- 12% of its resting value during cooling (28.8 +/- 4.8 degrees C (mean +/- S.D.) baseline versus 22.1 +/- 6.4 degrees C in the fifth minute of cooling, P = 0.012); this was accompanied by a reduction in capillary blood cell velocity similar to that described previously in cooling experiments using cold air (baseline median, 671 microns s-1 (range, 29-4421 microns s-1) versus median during cooling, 221 microns s-1 (range, 6.7-2579 microns s-1), P = 0.012). 4. The magnitude and timing of the capillary pressure response to cooling and recovery varied between individuals. In the group as a whole, there was no significant fall in capillary pressure during cooling (basal before cooling, 16.7 +/- 3.7 mmHg versus minimum during cooling, 15.1 +/- 3.5 mmHg, P = 0.12), whereas capillary pulse pressure amplitude was reduced (basal before cooling, 5.3 +/- 3.1 mmHg versus minimum during cooling, 3.7 +/- 2.6 mmHg, P = 0.028). 5. During the recovery phase, post cooling, both capillary pressure and capillary pulse pressure amplitude were markedly elevated compared to baseline or the cooling phase.(ABSTRACT TRUNCATED AT 250 WORDS)