The bioavailability of chondrosine was evaluated by its direct measurement as found in the blood plasma following removal of plasma proteins by perchloric acid. The postcolumn HPLC determination of chondrosine was performed on an SCX column (6 mm i.d.×150 mm), 0.35 mol/l boric acid (pH 5.2 adjusted by 0.1 mol/l NaOH) as an eluent (0.9 ml/min), 0.5% 2-cyanoacetamide and 1.0 M NaOH as fluorogenic reagents (0.25ml/min each) with a fluorescence detector (ex. 331nm, em. 383nm). Two separate animal studies were conducted. In study 1, adult male ddY mice (n=6) received i.v. chondrosine (1.0mg/kg body weight) and the plasma samples were collected. In the second study, 6 adult male ddY mice received p.o. chondrosine (400mg/kg body weight) and the plasma samples were collected. Blood plasma samples were deproteinized by perchloric acid, analyzed and the bioavailability of chondrosine was determined. Twenty five to fifty microliters of blood plasma were required for the assay. Chondrosine was absorbed after oral administration with two phases having two maximum values, 7.8±5.4 and 4.0±1.9 at 15μg/ml and 120min, respectively; it disappeared from the blood flow very quickly after intravenous administration. This study provides the first report of the bioavailability of orally administered chondrosine in mice.