In order to investigate the effect of age at weaning and the post-weaning environment on the behaviour and health of piglets, litters were weaned at 4 or 6 weeks of age and either kept in their farrowing pen or housed in flat decks (2 × 2 factorial design with a total of 24 litters). At 9 weeks of age all litters were moved to standard pens for fattening pigs. Behavioural observations and recording of lesions were undertaken at 8 and 12 weeks of age.