In initial studies the dose-limiting toxicity of paclitaxel monotherapy was leukopenia. In these studies, paclitaxel was administered over 24 hrs. The aim of the present phase II clinical trial was to investigate the efficacy and the hematological toxicity of a 3 hr paclitaxel infusion in previously untreated patients with NSCLC. Patients received 4 cycles of a chemotherapy consisting of paclitaxel 225 mg/m2 every three weeks. 30 patients (7 female, 23 male) were enrolled in the study. The characteristics of the patients are as follows: age 64 (47-75 yrs); histology: 19 x squamous cell carcinoma, 11 x adenocarcinoma: 4 x IIIB, 26 x IV; performance status 80 (70-90). After prior administration of an anti-allergic medication, hypersensitivity reactions after paclitaxel were not observed. After the first course of paclitaxel chemotherapy, hematological toxicity was as follows: leukopenia WHO-grade 1-2: n = 13; grade 3-4: n = 7; neutropenia grade 1-2: n = 9; grade 3-4: n = 12; anemia grade 1-2: n = 8; no significant thrombocytopenia. In all patients symptoms of peripheral neurotoxicity (WHO grade 1-2) were observed. 19 patients completed the intended four cycles of chemotherapy. The response rates were as follows: partial remission n = 8 (42%), no change n = 11 (58%). Among these patients, the 1-year survival rate was 63%. The efficacy of paclitacel monotherapy in patients with advanced NSCLC appears to be acceptable. The hematotoxicity of paclitaxel after 3h-infusion was markedly less compared to a 24h-regimen.