Granulocyte-colony stimulating factor (G-CSF), the most established agent for the mobilization of stem cells in current clinical practice, could induce a condition of oxidative stress. Herein plasmatic levels of protein carbonyl groups (a biomarker of oxidative stress) were measured in a group of donors given recombinant human G-CSF (rHuG-CSF) at different times: (1) before starting rHuG-CSF administration, (2) on day 5 of rHuG-CSF administration, (3) on the same day immediately after the end of the first leukapheresis procedure and (4) one week after rHuG-CSF withdrawal. Plasma levels of protein carbonyl groups enhanced significantly in donors after 5 days of rHuG-CSF treatment and appeared further slightly increased following leukapheresis procedure; 7 days following rHuG-CSF withdrawal, they showed a tendency to normalization. These findings may contribute to better understand the oxidative reactions following rHuG-CSF treatment and leukapheresis.