Background: BR and CHOP+/-R regimens are considered an intermediate FN risk (10-20%) per guidelines. Patients (pts) receiving these regimens need to be assessed for FN prophylaxis using specific risk factors. Current guidelines suggest waiting 24 hours post chemotherapy (CTX) to administer PFG due to an increased FN risk. Studies have shown equivocal outcomes between same day (D1) and next day (D2) administration. We evaluated real-world outcomes associated with D1 and D2 PFG administration in pts with lymphoma and CLL treated with these two regimens. Methods: Retrospective chart review of lymphoma or CLL pts treated with CHOP+/-R or BR and PFG or a biosimilar from 11/2013 through 11/2020 at the University of Arizona Cancer Center was conducted. Two pt cohorts were analyzed based on D1 vs D2 PFG administration timing. Outcomes of interest were the incidence of FN across all CTX cycles and after cycle 1, CIN grade 3/4, hospitalizations, antibiotics administration, and CTX dose reduction or delay. A secondary analysis compared the incidence of FN in pts receiving CHOP+/-R in our study with published studies (Burris et al, 2010 and Cheng et al, 2014) of D1 PFG in lymphoma pts. Results: Of the 116 pts meeting inclusion criteria, 103 received PFG on D1 and 13 on D2 of CTX. As shown in the Table, the incidence of 1st cycle FN was 6% vs 8% (P>0.05), FN across all cycles was 4% vs 5% (P>0.05), CIN grade 3/4, hospitalization, anti-biotic administration and dose delays/reductions incidences were 11% vs 16% (P>0.05), 8% vs 11% (P>0.05), 6% vs 32% (P=0.001), 11% vs 5% (P>0.05) for D1 vs D2, respectively. The incidence of 1^st cycle FN in D1 cohort was 6% vs 19% (P=0.15) and 11% (P=0.67) in our study vs Burris et al and Cheng et al, respectively. While the incidence of FN across all cycles in D1 group was 5% vs 9% (P=0.03) and 17% (P=0.001) in our study vs Burris et al and Cheng et al, respectively. Conclusions: This data provides evidence that D1 PFG/PFG-cbqv does not increase FN or delayed engraftment risk as compared to previously published studies in lymphoma and may be safe to use after CTX has been administered.