The pharmacokinetic behaviour of vinyldithiins, the main constituents of oily preparations of garlic (Allium sativum L.), was investigated after oral administration of 27 mg 2-vinyl-4H-1,3-dithiin and 9 mg 3-vinyl-4H-1,2-dithiin to rats. In serum, kidney, and fat tissue, both vinyldithiins could be detected by GC-MS over a period of 24 h, whereas in liver only 1,3-vinyldithiin was found. Pharmacokinetic parameters (t1/2, ke, Cltot, AUC, and Vd) were determined using compartment models, elucidating the different pharmacokinetic behaviour of both vinyldithiins. 1,3-Vinyldithiin seems to be less lipophilic and is rapidly eliminated from serum, kidney, and fat tissue, whereas 1,2-vinyldithiin is more lipophilic and shows a tendency to accumulate in fat tissue. Experiments with liver homogenate confirmed the in vivo findings on the different degradation rates of both vinyldithiins. Allicin, the precursor of the vinyldithiins, is metabolized more rapidly in liver homogenate than the vinyldithiins.