Background: Neutropenia is a common hematologic Grade (Gr) 3+ adverse event (AE) recorded in patients with chronic lymphocytic leukemia (CLL) receiving venetoclax (VEN). In this analysis, we evaluated fixed duration VEN monotherapy given to patients with relapsed or refractory (R/R) CLL with and without pre-existing Gr3+ neutropenia. Methods: This post-hoc analysis pooled data from patients in the ongoing Phase 3b trials VENICE-I and VENICE-II with R/R CLL who had received ≥1 dose of VEN monotherapy (ramp-up to 400 mg QD). Gr4 hematologic AEs and Gr3+ neutropenia ( < 1000 cells/mm³) with infection or fever were managed using dose interruption/reduction. Granulocyte colony stimulating factor (G-CSF) was used in Gr3+ neutropenia. Results: At data cutoff (June 30, 2019), 44/468 (9%) patients had Gr3+ neutropenia at baseline (BL; Gr3+ neutropenia group), 80% of whom received G-CSF during the study vs 38% of those with < Gr3 neutropenia at BL ( < Gr3 neutropenia group). Median on-study duration for VEN was 20.2 months (range: 0.1–36.1). Median number of prior CLL therapies was 2 for both groups (range: 1–10). Serious infections were experienced by 10/44 (23%) and 69/424 (16%) of patients in the Gr3+ and < Gr3 neutropenia groups, respectively. The most common AEs leading to discontinuation overall were second primary malignancies (13/468; 3%). 5/468 (1%) patients in the total population discontinued due to neutropenia/febrile neutropenia. One case of Gr5 infection with concomitant Gr3 neutropenia was reported in the < Gr3 neutropenia group post-VEN discontinuation. See Table. Conclusions: In this large post-hoc analysis, discontinuation due to neutropenia was rare (1%) in the overall population and accounted for 3/11 AE discontinuations in the Gr3+ neutropenia group; 10 patients had a serious infection. Patients with pre-existing neutropenia can be managed on VEN, though concurrent use of G-CSF is likely to be required. Additional data to follow. Clinical trial information: NCT02756611; NCT02980731.