Many studies have shown how laying aviaries can improve hens' welfare, but little work has been done on the adaptation of hens to this system according to their previous rearing conditions, despite the specific adaptation skills it requires of them. The adaptation to laying aviaries of hens previously reared in different conditions was assessed here through their use of vertical levels, numbers and distances of flights and jumps (in week 20 after transfer and, only in rearing aviaries, in week 15 before transfer), eggs location and laying rate (from weeks 18 to 27 after transfer) and mortality (from weeks I to 27). Twelve batches of 282-308 ISA Brown hens were reared from 1 day to 17 weeks of age in floor pens furnished with platforms and perches with manual feed hoppers on litter (FH hens), in rearing aviaries with platforms and manual feed hoppers on litter (AH hens), or in rearing aviaries with automatic chain troughs on platforms (AC hens). Hens in each of these treatments were then transferred to similar laying aviaries with automatic chain troughs on platforms. The FH hens used upper levels less, showed lower accuracy in long flights and jumps and displayed a preference for staying on litter and lower levels, compared with AH and AC hens. They laid fewer eggs inside nest boxes during the first 2 weeks of lay, laid more eggs on litter throughout the observed period, and had a lower onset of laying than AH and AC hens. The FH mortality rate was higher than that of AC hens after transfer, and higher than that of AH and AC pallets before transfer. AH pullets used the lower levels more and made more and longer flights than AC pullets before transfer, but these differences did not persist after transfer. Mortality rates did not differ between AH and AC pullets before transfer, whereas it was higher in AH hens after transfer. AH hens laid slightly more eggs inside nest boxes and had a similar laying rate to AC hens. The present study shows that the design of rearing pens largely influences adaptation: rearing aviaries ensured a better adaptation than furnished floor pens. On the other hand, the feeding system used during the rearing period, particularly troughs location, largely influenced the use of space before transfer, but only slightly influenced the adaptation after transfer in laying aviaries: higher vertical distance between feed and water ensured a better adaptation. (C) 2007 Elsevier B.V. All rights reserved.