Genetically modified maize hybrid MON 810, which contains a gene for the insecticide protein Cry1A(b), and a conventional non-modified hybrid were tested in three experiments whose objective was to determine their influence on slaughter, haematological and biochemical indicators of ROSS 308 broiler chickens. The chickens were fed a mixture containing 30.0-35.0% of maize. The nutrional contents in the Bt maize and standard maize were not significantly different. The experimental and control groups gave optimal results in terms of mortality and feed consumption per kg weight gain. The slaughter weight of the chickens at the age of 42 days in the control group and in the group fed with Bt maize fell within the range of 1.800 to 2.000 g in all three experiments. The results did not show any changes in yield parameters of the broiler chickens. The measured slaughter, haematological and biochemical parameters were not negatively affected by blending Bt maize into the feed mixtures. The haematological and biochemical parameters were found to be within physiological range with no significant changes.