A four-generation study with at least 60 laying hens (LSL) and 10 cockerels (LSL) was carried out to investigate the influence of genetically modified maize (Bt 176) on animal health and feed intake, laying performance, feed efficiency, and hatchability of chickens and to compare GM-maize with its near isogenic counterpart. The chickens were divided into two groups (one pen/group) of at least 30 hens each and 3 cockerels. The diets contained 400 (chickens and pullets) or 500 g · kg^–1 (laying hens) isogenic or genetically modified maize (Bt 176), respectively. Feed and water were provided ad libitum. Eggs for hatching were collected when the laying hen was aged 31 weeks. In the 31^st week of life, brooding eggs were collected and brooded for every group. One-day-old chickens from each group were sex sorted and allocated to one pen per group. There were no significant differences in composition between the two maize varieties. For every generation, as well as the average of all four generations, there was no significant influence on the feed intake of chickens (32.2 and 32.0 g per day), pullets (68.4 and 70.4 g per day) and layers (114.9 and 112.9 g per hen per day for control and Bt-maize), body weight of chickens (652 and 636 g), pullets after 18 weeks (1316 and 1305 g), and laying hens after 31 weeks (1656 and 1626 g for control and Bt-maize), laying intensity (83.5% and 83.3%), fertility of eggs (96.6% and 97.5%), or hatchability of living chicks (86.8% and 88.0% for control and Bt-maize). In conclusion, feeding of 400 (grower) or 500 g · kg^–1 (layer period) Bt-maize to chickens, pullets and laying hens for four generations did not significantly influence feed intake, growth, laying or breeding performance compared with an isogenic counterpart.