Tissue blood flow has been measured in Zucker lean and obese mts during treadmill exercise and later recovery, by using a fluorescent-dyed latex microsphere method. The procedure used allowed up to six different timed blood Slow measurements in the same animal. Exercise resulted in grossly increased muscle blood flow, compensated by lowered intestinal and liver irrigation. At the onset of fatigue, and during early recovery, liver portal blood flow increased in detriment of muscle. Obese rats showed a similar pattern, but their intestinal and hepatic blood flow was maintained during recovery, in contrast with lean rats. In obese - but not in lean - rats, skin blood flow increased in post-exercise recovery to disposal of excess heat hampered by blubber insulation. Metabolic inability to recover markedly affects post-exercise haemodynamics in Zucker obese rats, thus prolonging the consequences of fatigue. [References: 36].