An economic evaluation of paclitaxel added subsequently to doxorubicin plus cyclophosphamide (AC) adjuvant therapy for early breast cancer with lymph nodes positive is presented. Health care cost associated with AC alone vs. AC with paclitaxel was compared under Thai health care context. Based on CALGB9344, paclitaxel increased the disease-free survival (DFS) by 17%. Based on Markov simulation for 15 years, paclitaxel prolonged the patient's life by 0.30 quality-adjusted life years (QALY). Such an increased effectiveness was offset by the adjuvant cost net of recurrence, follow-up, and terminal care by 221,433 Baht. This means an additional year of perfect health gained by paclitaxel is achieved through an incremental cost of 738,111 Baht. Such an incremental cost-effectiveness ratio (ICER) is beyond the threshold recommended by World Health Organization. In women with negative estrogen receptor that DFS was improved to 28%, the ICER of paclitaxel was reduced to 393,984 Baht per QALY.