Febrile neutropenia and anemia are two major complications of chemotherapy. Human recombinant cytokines as G-CSF and erythropoietin allow efficient fight against these secondary effects but require iterative injections due to a short half life. The glycosylation of natural cytokines results in enhanced stability of these molecules of new generation and makes it possible to space the injections which become concomitant of chemotherapies. With regard to the erythropoietin, the prolonged half-life form shows a similar effectiveness with the natural molecule. For the G-CSF, the glycosylated form could still show itself more effective for the prevention of febrile neutropenias. Finally, these new molecules allow an improvement of the quality of life while ensuring an optimal dose-intensity of the treatment.