Background: Docetaxel is a widely accepted second-line treatment in advanced non-small-cell lung cancer (NSCLC) with a risk of myelotoxicity. This study evaluated the efficacy and toxicity profile of two docetaxel regimens in NSCLC patients who had failed first-line non-docetaxel-based chemotherapy. Patients and methods: A total of 259 patients from 33 Spanish centers were randomized to receive either docetaxel 75 mg/m2 administered every 3 weeks (3W arm) or docetaxel 36 mg/m2 given weekly (1W arm) for 6 weeks followed by 2 weeks of rest. The primary end point was 1-year survival; secondary end points were median survival, time to progression, response and toxicity. Results: One-year survival was 27% in the 3W and 22% in the 1W arm. Median time to progression was also similar in the two arms. Median survival was 6.6 months in the 3W arm versus 5.4 months in the 1W arm (P = 0.075). Response rates were 9.3% in the 3W arm and 4.8% in the 1W arm. More patients in the 1W arm experienced mucositis 1W, nine patients (7.2%); 3W, two patients (1.6%); P = 0.032, while febrile neutropenia was significantly higher in the 3W arm 3W, 10 patients (7.8%); 1W, one patient (0.8%); P = 0.010. Conclusions: Both weekly and 3-weekly docetaxel were effective and well-tolerated, with different toxicity profiles. In general, there was no indication to recommend the weekly schedule. However, the significant lower rate of febrile neutropenia observed in the weekly schedule makes it a good alternative for patients at risk of severe neutropenia.