Between 1980 and 1994, 71 women with histologically proven ductal carcinoma in situ (DCIS) were diagnosed at Ullevål Hospital; bilateral tumours were found in two patients. Surgical treatment was mastectomy (42 lesions) or local excision (31 lesions). Median follow-up time was 7.2 years. Ten patients experienced a local recurrence, seven of which were invasive carcinomas. The actuarial 5-year local recurrence rate was 22% after local excision. A multivariate analysis found that tumour size was the only factor that predicted local recurrence after local excision. An analysis of relative survival in a nation-wide material of 832 DCIS patients in the period 1980 to 1994 demonstrates that relative survival after a DCIS diagnosis is almost 100%, irrespective of surgical treatment of the initial lesion.