Evaluation of alterations in the level of alpha2-globulin in the serum of 18 patients with prostatic cancer prior to and following cryotherapy of their primary prostatic tumor and the clinical response of these patients disclosed: (1) a progressive increase in the level of alpha2-globulin and the incidence of patients with significantly elevated levels of alpha2-globulin, i.e., greater than or equal to 1.30 g/100 ml, with a progression of the stage of their malignancy; (2) a decrease in the levels of alpha2-globulin in the serum of 14 of 18 (78%) patients following cryotherapy, and (3) a favorable clinical response in 11 of 14 (79%) patients with prostatic cancer showing a decrease in alpha2-globulin following cryotherapy. While limited to the study of a relatively small patient population, the present results suggest a prognostic potential for alpha2-globulin, particularly as applied to stage identification in prostatic cancer. Pending confirmation by evaluation of a larger patient population, it may even provide objective criteria for monitoring the clinical response of an individual following cryotherapy of the prostate.