Pressure-diameter relationships of segments of human finger arteries, aged 57-85 years, were measured in vitro. The arteries, obtained at autopsy within 48 h after death, were stored in glucose-free Tyrode at 4 degrees C. Experiments began within 40 h after autopsy. The diameter responses to various transmural pressure changes, with and without the addition of noradrenaline to the Tyrode solution in the specimen chamber, were compared with the responses of freshly excised rat tail arteries. In general, pressure-diameter relations of human finger artery segments were similar to those of rat tail artery segments, with a steep slope in the collapse region near zero pressure. Also, spontaneous rhythmic contractions and myogenic activity induced by high transmural pressures were similar to those observed in the fresh rat tail arteries. Human finger arteries, however, could contract to complete closure both spontaneously and after addition of noradrenaline, while rat tail arteries did not. The diameter changes of the arterial segments during forced 1 Hz oscillations of 20-50 mm Hg (2.7-6.7 kPa) amplitude superimposed on a mean transmural pressure were substantially smaller than those during quasi-steady inflation-deflation ramps over the same pressure range, indicating the presence of a strong viscous wall component. Chemicals/CAS: noradrenalin, 1407-84-7, 51-41-2; Norepinephrine, 51-41-2