The radioactive components present in plasma proteins and adipose tissue after oral dosing of 14C-geranylgeranylacetone (GGA) to rats were characterized by gel filtration, paper electrophoresis, t.l.c. and reversed-phase column chromatography. The radioactivity associated with the plasma proteins was identified as 14C-labelled amino acids (Glu, Asp, Ala, Pro, Gly and probably Ser); however, no 14C was detectable in the essential amino acids. Radioactivity accumulated in adipose tissue as 14C-labelled fatty acids of triglycerides. The incorporation of 14C into amino acids and fatty acids may be due to the formation of 14C-propionyl-CoA resulting from omega-oxidation and successive beta-oxidations of 14C-GGA. This view was supported by the finding that 14C-acetate was incorporated into amino acids and fatty acids in a similar manner to 14C-GGA.