The response of skin blood cell flux (SBF) to locally applied pressure was evaluated by laser Doppler fluxmetry over the sacrum and the gluteus maximus muscle in twenty patients with spinal cord injuries (SCI)-ten with tetraplegia, ten with paraplegia-and ten healthy subjects. The SCI patients were further divided into two subgroups, one with sensation and the other without sensation over the sacrum area. The SBF over the sacrum, without applied pressure, showed somewhat higher values among the patients. The ten paraplegic patients (p less than 0.05) and the subgroup of patients without sensation over the sacrum (p less than 0.05) showed the highest values. Occlusion of the SBF was reached at a lower external skin pressure over the sacrum than over the gluteus maximus muscle in the group with spinal cord injuries (p less than 0.01). During the postocclusive reactive hyperemia we found a much shorter time to peak SBF over the gluteus muscle for the patients compared to the healthy subjects (p less than 0.01). In the subgroup of patients without sensation over the sacrum a prolonged time to peak SBF was found (p less than 0.01) over the sacrum compared to patients with sensation and to healthy subjects. The increase of the SBF during postocclusive hyperemia response was lower over both the sacrum and the gluteus maximus muscle areas in the patients with spinal cord injuries (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)