Daily granulocyte colony-stimulating factors [(G-CSFs); e.g. filgrastim, lenograstim] are frequently used to reduce the duration of chemotherapy-induced neutropenia (CIN) and the incidence of febrile neutropenia (FN) in cancer patients. A pegylated formulation of filgrastim, pegfilgrastim, which is administered once per cycle, was introduced in Spain in 2003. LEARN was a multi-centre, retrospective, observational study in Spain comparing patterns of use of daily G-CSF and pegfilgrastim, and CIN-related outcomes in adults with non-myeloid malignancies receiving myelosuppressive chemotherapy. Outcome measures were the percentage of patients receiving G-CSF for primary prophylaxis versus secondary prophylaxis/treatment, duration of treatment with G-CSF and incidence of CIN-related complications. Medical records from consecutive patients with documented pegfilgrastim (n = 75) or daily G-CSF (n = 111) use during 2003 were included. The proportion of patients receiving primary or secondary prophylaxis was comparable between the pegfilgrastim (39 and 48% respectively) and daily G-CSF (40 and 48% respectively) groups. However, there was a trend towards less frequent use to treat a neutropenic event such as FN or neutropenia in the pegfilgrastim group (17 versus 30% with daily G-CSF). Chemotherapy-induced neutropenia-related complications were less frequent in patients receiving pegfilgrastim (e.g. FN 11 versus 24% with daily G-CSF). This is the first study to show the potential benefits of pegfilgrastim over daily G-CSF in Spanish clinical practice.