PURPOSE To evaluate trastuzumab (H) and docetaxel (T) with or without capecitabine (X) as first-line combination therapy for human epidermal growth factor receptor 2 (HER2) -positive advanced breast cancer. PATIENTS AND METHODS Patients with HER2-positive locally advanced or metastatic breast cancer were randomly assigned to H (8 mg/kg loading; 6 mg/kg every 3 weeks) plus T (75 mg/m(2) in HTX arm, 100 mg/m(2) in HT arm, every 3 weeks) with or without X (950 mg/m(2) twice per day on days 1 to 14 every 3 weeks). The primary end point was overall response rate (ORR). Results In 222 patients, median follow-up was approximately 24 months. ORR was high with both regimens (70.5% with HTX; 72.7% with HT; P = .717); complete response rate was 23.2% with HTX compared with 16.4% with HT. HTX demonstrated significantly longer progression-free survival: median 17.9 months compared with 12.8 months with HT (hazard ratio, 0.72; P = .045), which translates to a gain of around 5 months. Two-year survival probability was 75% with HTX compared with 66% with HT. Febrile neutropenia (27% v 15%) and grade 3/4 neutropenia (77% v 54%) incidences were higher with HT than HTX. Treatment-related grade 3 hand-foot syndrome (17% v < 1%) and grade 3/4 diarrhea (11% v 4%) occurred more commonly with HTX than HT. One case of congestive heart failure occurred in each arm. CONCLUSION HTX is an effective and feasible first-line therapy for HER2-positive locally advanced or metastatic breast cancer, although it should be reserved for patients with good performance status who are not receiving long-term steroids.