Objective: Cryopreserved hematopoietic stem cell (HSC) products have been associated with a number of infusion-related adverse events (AEs), ranging from mild to life threatening. These AEs have been mainly attributed to the cryoprotectant agent DimethylSulfoxide (DMSO), but there are many other contributing factors such as post-thaw cell aggregation and cell debris, lysis of granulocytes and red blood cells (RBC). Our aim was to evaluate the incidence of infusion-related AEs in cryopreserved grafts and analyze associated HSC product characteristics. Material and methods: A retrospective analysis of cryopreserved HSC infusions from July 2019 to July 2020 at our institution was performed. We collected data on apheresis and bone marrow HSCT products’characteristics, patients’demographics and AEs. Before infusion, patients received intravenous hydration and Diphenhydramine plus Hydrocortisone pre-medication per institutional protocol. HSC bags were thawed bedside by immersion in a water bath and infused immediately. Vitals signs were monitored at 15-minute intervals during the procedure until 1 hour after. AEs were reported by the assistant physician on an “fusion Monitoring form” the end of each infusion. Results: A total of 103 HSC transplants (HSCT) were analyzed. AEs were reported in 25 (24.2%) of HSC infusions, 21 of them (88%) in the autologous setting. More than one AE was reported in 40% of the HSCTs. Recipients were mostly female (68%), mean age was 41 (range 1–74 years) and most common diagnosis was multiple myeloma (36%), followed by non-Hodgkin lymphoma (28%). Mild adverse reactions such as halitosis (36%) and flushing (32%) were the most frequent AEs, followed by hypertension (28%), nausea and vomiting (24%), cough and dyspnea (20%). Other cardiologic AEs included tachycardia (8%), but it was self-limited and required no medication. No severe neurological events were reported; one patient presented with mild dizziness. Our analysis showed no grade 3 or above AEs. Median CD34+(106/kg), total nucleated cell count (108/kg) and RBC (mL/kg) was, respectively, 3.15 (IQR 1.16–4.16), 5.0 (IQR 2.25–8.0), and 0.21 (IQR 0.15–0.32). Data on total number of granulocytes was available in 17/25 HSC products, with a median of 145×103/uL (IQR 67.7–227.1). Median volume of infused product (mL) and DMSO (mL/kg) was 89 (IQR 69–97) and 0,12 (IQR 0.1–0.15). Discussion: Infusion-related AEs are fairly common both in the autologous and allogeneic HSCT setting and here we report an overall incidence of AE similar to most groups – usually ranging from 20%–30%. Toxicity during infusion is often attributed to DMSO, but other contributing factors should be considered, such as post-thawing time until infusion and red blood cell content. Conclusion: Close infusion monitoring and pre-medication, systematically reporting adverse events and analyzing HSC product characteristics before infusion are some important measures to be taken in order to minimize these events.