Abstract. The present research objective was to asses the difference of some biochemical, hematological, immune and pork composition parameters in two groups of pigs fattened in winter and summer season. Pig performance was assessed in vivo (fattening and slaughter value) and post mortem studies which showed a season to be a significant factor influencing a level of some hematological and biochemical indices. In winter period, fatteners blood displayed increased leukocyte and immunoglobulin content with decreased red blood cell concentration. Whereas the animals finishing in the summer season had a higher growth rate. As compared to the winter period, the fatteners were found to have a higher content of crude protein, cholesterol and triglycerides as well as GGT, AST and cholinesterase concentration. In both seasons, the finishing pig carcasses had similar level of valuable cuts. A fattening season did not affect the technological value of the slaughter material obtained.