Four hundred and thirty-four patients with infiltrative ductal carcinoma were treated by limited surgery and irradiation between January 1960 and December 1980. The median follow-up was 103 months. Retrospective pathological analysis of the primary tumor identified a subset of pathological parameters which were predictors of local breast failure and survival. Pathological predictors of local breast recurrence were: incomplete surgical excision (P less than 0.0001), lymphatic invasion (P less than 0.02) and presence of an extensive in situ component (EDISC) (P less than 0.03). Pathological predictors of survival were: incomplete surgery (P less than 0.007), size of the primary tumour (P less than 0.03), high histologic grade (P less than 0.005), lymphatic invasion (P less than 0.0001) and absence of associated in situ component (P less than 0.008). This study emphasizes the role of the in situ component in the prognosis of breast carcinoma treated with conservative management.