Effector cells such as eosinophils and mononuclear cells play crucial role in the mechanism of injury during acute renal allograft rejection (ARAR). The aim of the study was to evaluate an influence of tissue eosinophilia observed in the renal allograft biopsy (RAB) during ARAR on rejection severity (reversibility) as well as long-term graft function. The histopathological examination and the quantitative assessment was performed in 165 RAB with symptoms of ARAR. The numbers of eosinophils were counted at high power (40xobj), over the entire renal cortex, minimum 10 high power fields(hpf). Results. Significant tissue eosinophilia was found in 49 RAB (29%). In the Eosinophilic Group (EG) we observed: more frequent biopsy-confirmed ARAR episodes (1.79 vs. 1.33/pts; p=0.03), higher grade of acute rejection according to the Banff classification (p=0.007), more severe clinical course of rejection expressed as worse graft function at 6 month after treatment (serum creatinine 2.2 vs. 1.5 mg/dl). Chronic rejection was seen in 25% pts of EG and in 11% pts of Control Group (CG) in the first year after Tx. Graft survival at 6 month in the EG was shorter then in the CG (91% vs 96.3%). Conclusions. Eosinophilic infiltration of RAB is a negative predictor, which can indicate more severe course of ARAR and increased resistance to an anti-rejection therapy. It can determine an appearance of chronic allograft dysfunction hazard.