Speciation of Pr(III) in human blood plasma has been investigated by computer simulation. The speciation and distribution of Pr(III) has been obtained. It has been found that most of Pr(III) is bound to phosphate and to form precipitate. The results obtained are in accord with experimental observations. Speciation of Pr (III) in human blood plasma has been investigated by computer simulation. The speciation and distribution of Pr (III) has been obtained. It has been found that most of Pr (III) is bound to phosphate and to form precipitate. The results obtained are accordant with experimental observations.