Capillary blood cell velocity was measured in a group of normotensive febrile patients as a basis for further study into the microvascular physiology of febrile hypotensive patients with sepsis. Television videomicroscopy was used to record the capillary blood cell movement in the finger nailfold. Analysis of all moving gaps in the red cell column seen during a minimum of 2 minutes was done by the frame-by-frame technique and mean blood cell velocity derived. Core (external auditory meatus) and skin (finger) temperature were also measured. Subjects (n = 6) were sex and skin temperature matched to controls. Although the mean skin temperature of subjects [28.73 degrees C, SD = 0.28] was not significantly different to controls [30.63 degrees C, SD = 3.11; p less than 0.05] the mean velocity was significantly reduced in the febrile subject group [0.28 mm/sec, SD = 0.17] as compared with controls [0.56 mm/sec, SD = 0.22; p less than 0.05]. It is likely therefore that these skin vessels vasoconstrict as part of the integrated response to reduce heat loss.