['Bone marrow concentrate (BMC) and platelet-rich plasma (PRP) are used extensively in regenerative medicine. The aim of this study was to determine differences in the cellular composition and cytokine concentrations of BMC and PRP and to compare two commercial BMC systems in the same patient cohort.', 'Patients (29) undergoing orthopaedic surgery were enrolled. Bone marrow aspirate (BMA) was processed to generate BMC from two commercial systems (BMC-A and BMC-B). Blood was obtained to make PRP utilizing the same system as BMC-A. Bone marrow-derived samples were cultured to measure colony-forming units, and flow cytometry was performed to assess mesenchymal stem cell (MSC) markers. Cellular concentrations were assessed for all samples. Catabolic cytokines and growth factors important for cartilage repair were measured using multiplex ELISA.', 'Colony-forming units were increased in both BMCs compared to BMA (p\xa0<\xa00.0001). Surface markers were consistent with MSCs. Platelet counts were not significantly different between BMC-A and PRP, but there were differences in leucocyte concentrations. TGF-β1 and PDGF were not different between BMC-A and PRP. IL-1ra concentrations were greater (p\xa0=\xa00.0018) in BMC-A samples (13,432\xa0pg/mL) than in PRP (588\xa0pg/mL). The IL-1ra/IL-1β ratio in all BMC samples was above the value reported to inhibit IL-1β.'] Do bone marrow concentrate and platelet-rich plasma differ in cell distribution and interleukin 1 receptor antagonist protein concentration?