In patients with hematological diseases, there is a different kind of treatment, the autologous stem cell transplant (ASCT) is a potentially useful and beneficial alternative. to perform an ASCT high dose of chemotherapy are required, which would generate severe pancytopenia, and sometimes complicated by febrile neutropenia (FN) and infections, generating a significant increase in morbidity and mortality, in costs and deterioration of patients quality of life. our objective is; to determine the differences regarding the therapeutic response of Pegfilgrastim (PEG) initiated day+1 versus day +5 in patients undergoing an ASCT in the Imbanaco Medical Center. Materials and Methods: retrospective cohort analytical study, comparing a historical cohort of patients who received PEG (6mg/0.6ml) day +5 between January/2013 to March/2015 after ASCT, compared to a cohort that started PEG (6mg/0.6ml) day +1 between Mayo/2015 to June/2016. for the results, evaluation we used the following endpoints: days of recovery of the absolute neutrophil count (ANC), FN, hospital readmissions, day +100 post-transplant mortality. results: the two cohorts day +5 and day+1 with (n=41), (n= 35) patients respectively, the age average was 56.6 years (range 24-72), the most frequent diagnoses were multiple myeloma, Hodgkin's and non-Hodgkin's lymphomas. the recovery of the ANC>500/mm3 was on average on day+11 and +12 figure.1 (HR: 2.39; (p=>0.05) in the PEG+1 and PEG+5 groups, respectively; the incidence of FN was 50%(p=0.026) in both cohorts. when compared regarding hospital readmissions group day+5 presented 7.3% (3/41) vs 0% (0/35) of group day+1. no cases of mortality 100 days post-transplant were reporting in both groups. any report of infections during the inpatient therapy in both groups. conclusions: administering PEG on day+1 shortened the ANC > 500 /mm3 recovery day by at least one day, maintaining the same efficacy of the therapy with respect a similar incidence of FN, infections and 100 days post-transplant mortality associated with transplantation with PEG day +5. the final results of the analysis of this study will be present at the congress. In patients with hematological diseases, there is a different kind of treatment, the autologous stem cell transplant (ASCT) is a potentially useful and beneficial alternative. to perform an ASCT high dose of chemotherapy are required, which would generate severe pancytopenia, and sometimes complicated by febrile neutropenia (FN) and infections, generating a significant increase in morbidity and mortality, in costs and deterioration of patients quality of life. our objective is; to determine the differences regarding the therapeutic response of Pegfilgrastim (PEG) initiated day+1 versus day +5 in patients undergoing an ASCT in the Imbanaco Medical Center. Materials and Methods: retrospective cohort analytical study, comparing a historical cohort of patients who received PEG (6mg/0.6ml) day +5 between January/2013 to March/2015 after ASCT, compared to a cohort that started PEG (6mg/0.6ml) day +1 between Mayo/2015 to June/2016. for the results, evaluation we used the following endpoints: days of recovery of the absolute neutrophil count (ANC), FN, hospital readmissions, day +100 post-transplant mortality. results: the two cohorts day +5 and day+1 with (n=41), (n= 35) patients respectively, the age average was 56.6 years (range 24-72), the most frequent diagnoses were multiple myeloma, Hodgkin's and non-Hodgkin's lymphomas. the recovery of the ANC>500/mm3 was on average on day+11 and +12 figure.1 (HR: 2.39; (p=>0.05) in the PEG+1 and PEG+5 groups, respectively; the incidence of FN was 50%(p=0.026) in both cohorts. when compared regarding hospital readmissions group day+5 presented 7.3% (3/41) vs 0% (0/35) of group day+1. no cases of mortality 100 days post-transplant were reporting in both groups. any report of infections during the inpatient therapy in both groups. conclusions: administering PEG on day+1 shortened the ANC > 500 /mm3 recovery day by at least one day, maintaining the same efficacy of the therapy with respect a similar incidence of FN, infections and 100 days post-transplant mortality associated with transplantation with PEG day +5. the final results of the analysis of this study will be present at the congress. Figure 1.