We retrospectively analyzed the effects of dosages of docetaxel (DOC) in combination chemotherapy with carboplatin (CBDCA) against advanced non-small cell lung cancer (NSCLC). Twenty-three cases of previously untreated NSCLC (stage III and IV, performance status: 0-1) that were pathologically or cytologically confirmed were divided into 2 groups (DOC-60, DOC-70) based on their received DOC doses (60 and 70 mg/m2, respectively). Both groups had similar patient characteristics and received similar treatment except for their DOC doses. Although not statistically significant, the response rates after the completion of whole cycles of the treatment (mean: 4 cycles) were 18.2% in DOC-60 and 41.6% in DOC-70. Leukocytopenia, neutropenia and anemia were observed similarly in both groups. However, while thrombocytopenia was not observed in DOC-70, it was found in 36.4% of the cases in DOC-60. In combination chemotherapy with carboplatin against advanced NSCLC, the use of DOC at 70 mg/m2 was rather protective against thrombocytopenia, keeping the response equivalent or possibly superior to that obtained in the patients treated with DOC at 60 mg/m2.