Purpose <p>Febrile neutropenia (FN) is a common side effect of chemotherapy. It may be prevented by granulocyte colony-stimulating factors (G-CSF), requiring customization based on patients’ risk factors, the type of cancer and chemotherapy, and the formulation used. This observational study investigated all-day use of a pegfilgrastim formulation, also available for self-administration.</p> Methods <p>In outpatient clinics across Germany, doctors recorded data of adult patients suffering from a malignant disease routinely treated with chemotherapy and pegfilgrastim.</p> Results <p>Overall, 1636 patients received pegfilgrastim, predominantly women suffering from yet untreated breast cancer, 62% being at moderate and 38% at high risk of FN. In total, 2.5% of patients experienced FN despite treatment with pegfilgrastim, with 52.5% requiring hospitalization; in 40%, subsequent chemotherapy had to be postponed or reduced in dose. FN incidence and hospitalization rates were slightly lower when pegfilgrastim was given for primary versus secondary prophylaxis whereas there was no difference when given on day 1 or any later day following chemotherapy. FN incidence was much higher in patients with hematological as compared to solid tumors, particularly when treated with BEACOPP regimens. By contrast, related hospitalization depended less on cancer type and chemotherapy. Pegfilgrastim counterbalanced patients’ risk factors, but a previous FN episode and male sex still increased the risk of hospitalization. Overall, 13.4% of patients experienced infections. The most common side effect of pegfilgrastim was bone-related pain. The syringe and self-injector formulations showed comparable effectiveness and safety.</p> Conclusions <p>Pegfilgrastim (Pelgraz®) treatment appeared to be effective and safe in all-day practice.</p>