Isolated livers from rats fed a diet containing corn oil (10% W/W) perfused with a blood-free, modified Krebs-Henseleit solution cleared hexobarbital at a rate significantly faster than livers from rats fed a similar diet devoid of corn oil. The half-lives of hexobarbital in these experiments were 22.4 +/- 1.8 min for livers from rats fed corn oil and 30.0 +/- 1.2 min for those from rats fed the fat-free diet. This represented a metabolic rate of 54 microgram hexobarbital/g liver/min in fat-fed animals and 36 microgram hexobarbital/g liver/min in those fed a rat-free diet.