Abstract The effect of early rearing environment and tail docking on behaviour and production of fattening pigs was investigated in 576 cross-bred pigs. Half of the pigs came from four commercial pig units with tethered or otherwise confined sows, 4 weeks' weaning, little space per piglet and no use of straw. The other half of the pigs came from another four commercial units with loose-housed sows, 5-6 weeks' weaning and liberal space and use of straw. Half of the piglets from each of the units were tail docked. At an average weight of 33.5 kg the pigs were transferred to environmentally rich experimental pens where they stayed until slaughter at approx. 100 kg liveweight. On 8 observation days evenly distributed during the fattening period the pigs' use of the straw sections of the experimental pens was recorded as well as oral activities directed towards pen mates, including tail biting. The pigs' use of the pen's straw section declined significantly (p < 0.005) during the fattening period. The rearing environment had a significant effect on nibbling on pen mates (p <0.04) but not on tail biting. The nibbling on pen mates decreased (p < 0.02) while tail biting increased (p < 0.03) during the fattening period. The tail status had no significant effect on either of the two behavioural parameters. Neither rearing environment nor tail status influenced the relative growth rate. Pigs recruited from the “barren” environment showed an almost statistically significant higher incidence of chronic pleuritis (p = 0.069).