Both fundamental and clinical studies suggest that class III beta-tubulin expression is associated with resistance to taxanes and constitutes a prognostic factor in several solid tumors. In this study, we assessed the prognostic and predictive value of class III beta-tubulin in tumors of patients with locally advanced or metastatic non-small cell lung cancer (NSCLC) treated with paclitaxel-based or other regimens that did not include tubulin-binding agents. Expression of class III beta-tubulin was examined immunohistochemically in 91 tumor samples obtained before treatment from patients with stage III and IV NSCLC, including 47 who received paclitaxel-based regimens and 44 who received regimens without tubulin-binding agents. Response to chemotherapy, progression-free survival, and overall survival were correlated with the expression of class III beta-tubulin protein. The response rate was 37.5% (16 responses among 45 evaluable patients) among patients receiving paclitaxel. Patients whose tumors expressed low levels of class III beta-tubulin isotype had a better response rate, longer progression-free survival, and overall survival (P < 0.001, 0.004, and 0.002, respectively), whereas this variable was not found to be predictive in patients receiving regimens without tubulin-binding agents. A multivariate analysis taking into account sex, age, histology, stage, and class III beta-tubulin confirmed that low-level class III beta-tubulin expression was independently correlated with progression-free survival (P = 0.003) and overall survival (P = 0.003). These findings suggest that the expression levels of class III beta-tubulin in tumor cells is predictive of response to therapy and patient outcome in patients with NSCLC receiving paclitaxel-based chemotherapy but is not a general prognostic factor in this patient population.