Studies have suggested that environmental enrichment can improve the welfare of growing pigs through the provision of substrates for exploratory and manipulatory behaviour (Beattie et al., 2000; Petersen et al., 1995; Arey, 1993). EU Directive 2001/93/ EU states that pigs must have permanent access to materials such as straw, hay, wood, sawdust, mushroom compost and peat to enable proper investigation and manipulation. This extends the previous Directive 91/630/EEC which stated that: ‘‘ . . .all pigs . . .shall have access to straw or other material or object suitable to satisfy those [behavioural] needs’’. However, the suitability of different forms of enrichment is still the subject of debate. Straw can offer advantages for animal welfare due to its use as a recreational stimulus, a nutritional substrate and as bedding (Fraser et al., 1991). In barren rearing environments, the highly motivated oral activities of rooting and chewing tend to become re-directed towards penmates (e.g. Lyons et al., 1995;Kelly et al., 2000) and pen hardware (e.g. Lyons et al., 1995; Guy et al., 2002). Despite this, a recent review of housing systems in current use within the EU shows that the majority of finishing pigs are kept in buildings with slatted floors (Hendriks et al., 1998), with no access to straw for either bedding or occupation. The use of rooting materials, such as straw, in slatted systems can cause difficulties for slurry management and it is therefore important to establish whether alternative forms of environmental enrichment, such as hanging objects, can be equally effective. This study aimed to assess the effects of environmental enrichment with either hanging manipulable toys or rootable substrates on the behaviour of finishing pigs in two contrasting housing systems. Thousand one hundred and twenty four (Large White x Landrace) x Large White pigs were housed contemporarily in either a straw-based (ST) or fully slatted (FS) building from 35 kg to slaughter at 104 kg liveweight. In each building, half the pens received additional enrichment in the form of a hanging plastic toy (Bite-Rite). In the ST house only the straw bedding enriched the remaining pens. The remaining pens in the FS house were provided with hoppers containing shreds of unmolassed sugar beet pulp. The level of Bite-Rite manipulation was significantly higher in the FS system than in the ST system (P < 0.05). Within the FS system, the sugar beet pulp occupied the pigs for more time than the Bite-Rite object (P < 0.05). Neither object provided a level of occupation close to that of straw bedding in the ST system. In the absence of straw, more investigatory behaviours were directed towards pen components (P < 0.001); however, no significant differences in pig-directed behaviours were observed. Further study is required to identify functional forms of environmental enrichment for pigs in unbedded systems.