Evaluation of alterations in the level of the five major electrophoretic fractions of serum proteins (albumin, α1- a2-, β- and γ-globulin) in 18 patients with prostatic cancer prior to and following cryoprostatectomy disclosed: (i) a progressive increase in the level of α2- and β-globulin and the incidence of patients possessing statistically significant (p < 0.05) elevations in these proteins with a progression of the stage of their malignancy; (ii) a significant decrease in albumin, α2- and β-globulin and increase in α1- and γ-globulin from their preoperative levels following cryoprostatectomy in patients with metastatic disease (stage III) in association with a favorable clinical response; (iii) an overall significant decrease in albumin and α2-globulin and increase in α1-globulin from their preoperative levels, and (iv) a general association of decreases in albumin (83% of the patients) and α2-globulin (92%) and increases in α1-globulin (92%) and γ-globulin (75%) with a favorable clinical response following cryoprostatectomy. Limited to study of a small patient population, the present results confirm earlier studies suggestive of a prognostic potential for α2-globulin, as applied to stage identification in prostatic cancer once the initial diagnosis has been made. Pending confirmation and evaluation of a larger patient population, the observed alterations in serum proteins, while not pathognomonic for prostatic cancer, and alterations of inhibitory (‘immunoregulatory’) factors, may provide adjunctive criteria for monitoring the clinical response following cryoprostatectomy.