A series of 222 tumor samples stored at -80 degrees C in the authors' tumor library were investigated with anti-p53 (PA 1801) and streptavidin-biotin-peroxidase complex. The p53 immunoprecipitates were quantified by densitometry assessed by image analysis of digitized microscopic images. Two parameters, percentage of positive surface and mean optical densities, were compared with the patient's outcome (follow-up = 96.8 months) (life table method, Mantel Cox test, BMDP statistical software). The p53 expression significantly correlated with a poor overall survival (P = .0063), metastasis-free survival (P = .024), and recurrence-free survival (P = .022) at a 20% cutoff point of positive immunoreactive tumor surface. A strong prognostic significance was observed in the node-positive subset of patients but not in the node-negative subset, except for recurrence-free survival (P = .047). The results indicate the clinical relevance p53 evaluated by quantitative immunocytochemistry.