1. We studied: behavioural frequencies and time budgets of behaviour patterns in non-beak-trimmed White Leghorn layers housed in cages (720 cm2/hen, 3 hens/cage), and in the Marielund, the Tiered Wire Floor (TWF), and the Laco-Volétage aviaries (17 hens/m2 ground area); individual variation in behaviour among aviary hens; spatial utilisation of the different types of aviary. 2. At 25, 40, and 60 weeks of age behaviour patterns of 114 focal animals were data logged. Each bird was observed for 10 min 4 times a day on three consecutive days. 3. The frequency of activity transitions and the activity level was highest in TWF, second highest in cages, and lowest in Laco-Volétage, suggested that Laco-Volétage hens were the calmest, whereas birds in cages and in TWF were more restless. Abnormal types of behaviour occurred most often in cages and TWF. The disadvantageous behaviour patterns shown by birds in TWF and cages imply that these environments were the least appropriate for this layer strain. 4. Pronounced individual variations in mobility and facility utilisation were found, both within and between the three aviaries. Resting levels were used twice as much (Laco-Volétage), and litter areas one third as much (Marielund), as that expected on a simple a proportionate basis. Most feather pecking was performed at resting levels and on feeding floors, whereas most agonistic behaviour patterns were observed on feeding floors and litter. 5. Measures to improve the aviaries are outlined.