We studied factors predicting docetaxel-related toxicity in 113 unselected patients with metastatic cancer treated under routine daily practice. Docetaxel was administered in either a weekly, bi-weekly or tri-weekly schedule. All patients received prophylactic dexamethasone. Twenty-six patients were aged 70 or more, and 28 (24.8%) had an ECOG performance status (PS) score > or = 2. Primary tumors were mainly in breast, lung, and stomach (58, 25, and 14 patients, respectively). Most patients had metastases at two or more sites and were heavily pretreated. NCI-CTC graded toxicities were mild. Grade 3/4 leucopenia and neutropenia occurred in 19.4% and 10.6% of patients, respectively, with febrile neutropenia in 2 patients. Severe nonhematologic toxicities were rare, except for asthenia (8 patients). Complete alopecia occurred in 26.6% of patients. A proportional-odds regression analysis demonstrated that the tri-weekly schedule and older age represented independent risk factors for all-grade leucopenia, whereas a poor PS for anemia. Primary tumor in breast, tri-weekly schedule, an abbreviated and low dose of corticosteroids premedication, and high duration and cumulative dose of docetaxel were factors predicting asthenia. Risk factors for alopecia and vomiting were tri-weekly schedule and high docetaxel cumulative dose, respectively. In conclusion, in daily clinical practice docetaxel toxicity may be correlated with factors related to patient, disease, and treatment characteristics. Taking into account these variables could be a first step toward individualizing treatment.