We have analyzed 14 human urothelial cell lines in two different transformation grades for the production of a tumor-associated-alpha-2-macroglobulin. It has been shown in radioimmunoprecipitation and immunoblotting tests that human urothelial cells in vitro do not synthesize the wide-spectrum proteinase inhibitor alpha-2-macroglobulin. Four of the tested cell lines were additionally tested for the expression of specific mRNA which resulted in negative findings. The significance of the absence of alpha-2-macroglobulin in the human urothelial cells is discussed.