Thirty eight ductal carcinomas in situ of the female breast detected during the first 7 years of screening by the Guildford Breast Screening Unit have been treated by one surgeon. Twenty-eight cases were treated conservatively and ten by mastectomy. In the group treated conservatively there have been five local recurrences: four as ductal carcinoma in situ and one as node negative microinvasive carcinoma. There were no clinical or pathological features that predicted local recurrence, which was detected only by follow-up mammography. Based on these early results, an initially conservative approach to screen detected ductal carcinoma in situ is advocated.