OBJECTIVE The objective of this study was to identify the patients who are at low or high-risk by defining the prognostic factors in node-negative breast carcinomas. METHODS Medical records of 384 consecutive breast cancer patients with negative axillary lymph nodes who had been operated on between January 1994 and January 1997 at our hospital were retrospectively reviewed. Several clinical and pathological characteristics of patients were categorized. Univariate analyses of survival and disease-free survival (DFS) were performed by the Kaplan-Meier method and the log-rank test. Independent prognostic and predictive factors affecting survival and DFS were assessed by Cox proportional hazard method. RESULTS 5-year survival and DFS were 91.4 and 85.7%, respectively. Size, grade, age, and lymphovascular invasion (LVI) were the prognostic factors that independently affected survival and DFS. Tamoxifen improved survival and DFS. While age younger than 35 was an adverse factor for both survival and DFS, age older than 49 was a detrimental factor for DFS. CONCLUSIONS Patients who have a tumor with size greater than 2 cm, with histologic grade 3, with LVI, and patients with age under 35 or older than 49 have poorer prognosis among node-negative breast carcinomas, and are candidates for adjuvant therapy.