We retrospectively evaluated clinical data before therapy to determine the risk factors for severe neutropenia in advanced non-small-cell lung cancer (NSCLC) patients treated with third-generation agents. We analyzed 100 patients who received such agents (paclitaxel, docetaxel, gemcitabine, irinotecan, or vinorelbine) for advanced NSCLC. The endpoint of the survey was the occurrence of severe neutropenia (grade 4). Risk factors significantly related to severe neutropenia were identified using logistic regression analysis. Of the 100 patients studied, the median age was 62.0 (32-81 years), and 77 (77.0%) were male. CEA 6.6 (0-2220) ng/dL and cytokeratin 19 fragment 21-1 (CYFRA) 4.8 (0.2-173.8) ng/dL before chemotherapy were higher than normal range. Severe neutropenia occurred in 36.0%, the incidence being highest in the first cycle (61.1%). In the univariate analysis, variables associated with severe neutropenia were sex, chest pain, absolute neutrophil count (ANC), Cr, CRP, and CYFRA. In the multivariate analysis, low CYFRA level was identified as a significant risk factor that contributed independently to chemotherapy-induced severe neutropenia (p<0.05). Our analysis suggests that low CYFRA level is the most important risk factor for severe neutropenia in advanced NSCLC patients after the first course of chemotherapy with third-generation agents.