Patulin, a genotoxic mycotoxin produced by several species of Aspergillus, Penicillium and Bysochlamys is the most common mycotoxin in apples and apple-derived products. Patulin may be neurotoxic, immunotoxic, immunosuppressive, genotoxic, teratogenic and carcinogenic. The aim of the present study was to investigate the effect of patulin on chosen haematological parameters (red blood cells - RBC, white blood cells - WBC, platelets - PLT, haematocrit - HCT, haemoglobin - HGB) in porcine blood in vitro. Samples with patulin were incubated with patulin: 10 ng.ml-1 in E1 group, 100 ng.ml-1 in E2 group, and 1000 ng.ml-1 in E3 group for 4 hours at 37°C. The group without any addition served as the control. Patulin caused significant decrease of WBC in all experimental groups when compared to the control. In case of RBC patulin significantly decreased the number of RBC in porcine blood followed by increase of hemolysis and decrease of HGB and HCT in all experimental groups when compared with the control group. The count of PLT was significantly decreased in all experimental groups against the control. Results of this study provide a foundation for further analysis and researches on mycotoxins impact on living cells and the system of possible protection against its effects as well as evaluation of various dose dependencies on haematological parameters.