A consecutive series of 130 review-confirmed cases of noninvasive ductal carcinoma of breast (DCIS) in women without previous breast carcinoma was analyzed. Histologic variables assessed included histologic pattern, nuclear grade, necrosis, and involved duct counts. These were correlated with presentation, extent of DCIS in the breast, completeness of excision, and outcome. Comedo DCIS had an occult presentation significantly more often than noncomedo DCIS. Micropapillary DCIS was significantly more likely than other patterns to involve multiple quadrants of breast, irrespective of nuclear grade or necrosis. Solid DCIS was significantly more often completely excised when compared with all other patterns, while high-grade DCIS was significantly more often incompletely excised compared with low-grade DCIS. Follow-up showed invasive recurrence in 16% of cases treated by primary local excision only and 3% cases treated by mastectomy or with re-excision. Of local excision cases with follow-up longer than 3 years, 22% had invasive recurrence. Invasive recurrence only followed high-grade DCIS and most often followed comedo DCIS. The need for strict definition of categories of DCIS is stressed.