The feather pecking behaviour of four different genetic strains of hens was examined in an aviary system, starting at 38 weeks of age. The four genetic strains used in this study were Lohmann Selected Leghorns, Norbrid 41, Lohmann Brown and ISA Brown. The feather pecking behaviour was observed via video recording. In addition, the condition of the feathers, keel bone, bumble foot, body weight and length and curve of the beak were also recorded from week 17 until week 69. The medium heavy strains (Browns), especially the ISA Brown, performed the most feather pecking behaviour, especially when compared to the levels seen in the White Leghorn strains. The number of pecks performed during a single feather pecking incident was not significantly different amongst the various strains, however, when pecking was directed towards the back of another bird, the pecking bout lasted significantly longer in White Leghorn Strains. Specifically Lohmann Selected Leghorns pecked significantly longer at the ventral area of the body. For all four strains, a feather-pecking bout tended to last much longer if it was directed towards the tail. Time of day also affects feather pecking, as the number of feather pecks per hour increased as the day progressed, and this increase was more drastic in medium heavy strains. The condition of the skin became poor quite quickly once the hens began to lay, this was similar in all strains. In terms of condition of the feathers at the end of the laying period, Norbrids had the best and Lohmann Browns had the worst.