Capillary filtration rate (CFR) was measured by a mercury-in-silastic strain-gauge around the forefoot when the forefoot was lowered 40 cm below heart level. In seven normal limbs, CFR was 0.061 (0.049-0.086) ml (100 g min)-1 against 0.049 (0.016-0.071) ml (100 g min)-1 in 24 limbs with occlusive arterial disease (P = 0.01). About 8 days after arterial reconstruction CFR decreased to 0.039 (0.018-0.071) ml (100 g min)-1, but before 3 months after reconstruction CFR increased to normal values 0.061 (0.037-0.071) ml (100 g min)-1. The explanation offered for the reduced CFR before and immediately after arterial reconstruction is temporary thrombosis in the smallest distributing arteries and in the arterioles resulting in heterogeneous flow distribution and decreased fluid filtration in poorly perfused segments of the capillary bed. The results speak against increased capillary filtration as the aetiology of the post-reconstructive oedema.