['The infusion of thawed haematopoietic progenitor cells from apheresis (HPC-A) is associated with minor but frequent adverse reactions (ARs), which has been mainly attributed to dimethyl sulphoxide (DMSO). Nevertheless, other factors may play a role in the pathogenesis of such toxicity.', 'The ARs on a cohort of 423 cryopreserved HPC-A infusions for 398 patients in HPC transplantation program were analysed.', 'ARs were reported in 105 graft infusions (24·8%) and most of them were graded as mild to moderate. The most frequently reported ARs were gastrointestinal and respiratory, and three patients presented epileptic seizure. The volume of DMSO/kg (P < 0·001), volume of red-blood-cells/kg (P = 0·02), number of nuclear cells (NCs)/kg (P <0·001) and number of granulocytes/kg (P<0·001) in the infused graft were significant in the univariate analysis for the occurrence of ARs. The amount of granulocytes/kg remained significant in the multivariate analysis (P<0·001). The grade of ARs also correlated with the amount of cryopreserved granulocytes.'] Are adverse reactions during transfusion of thawed haematopoietic progenitor cells from apheresis closely related to the number of granulocyte cells in the leukapheresis product?