Pharmacokinetic studies of diosmin were performed after an oral administration to healthy volunteers. Diosmin and its aglycone, diosmetin, were determined by HPLC and LC-MS techniques. At least, at the level of sensitivity of our method, no parent compound was present in the plasma but only its aglycone, diosmetin. Analysis of the pharmacokinetic parameters showed that the drug was rapidly absorbed. Diosmetin presents a long plasma elimination half-life ranging from 26 to 43 hours. Our data show the total absence of urinary elimination for both diosmin and its aglycone diosmetin, while its minor metabolites are eliminated in the urine, mainly as glucuronic acid conjugates. The presence of degradation products such as alkyl-phenolic acids confirms a metabolic pattern similar to other flavonoids.