Exploration is a biologically important behaviour used to gain information about the surrounding environment and available resources (Wemelsfelder and Birke, 1997). Pigs have developed foraging strategies that depend on high levels of exploratory behaviour involving the mouth and snout (Arey, 1993). Current EU legislation (Directive 2001/93/EC) requires that ‘‘. . . pigs must have permanent access to a sufficient quantity of material to enable proper investigation and manipulation activities, such as straw, hay, wood, sawdust, mushroom compost, peat, . . .’’. Since the use of most particulate rooting materials in slatted systems can cause difficulties for slurry management, it is necessary to identify other forms of enrichment that meet the requirements of both the animal and the producer within the confines of the system as failure to provide adequate enrichment has been implicated in the development of adverse behaviours. In pens without bedding, exploratory behaviour is redirected towards pen-mates (Beattie et al., 2000; Kelly et al., 2000; Lyons et al., 1995) and pen components (Guy et al., 2002; Lyons et al., 1995). Tail-biting behaviour is also more prevalent under these conditions (Van de Weerd et al., 2005; Scott et al., in press). The aims of this experiment were to assess the effects of: (1) environmental enrichment with either straw bedding or a hanging manipulable toy and (2) the ratio of pigs to environmental enrichment when in the form of a hanging toy, on the behavioural responses and synchrony of behaviour in finishing pigs. One thousand and twenty four (Large White x Landrace) x Large White pigs were housed contemporarily, in 32 pen groups of 32 pigs (16 pens in each housing system), in matched straw-bedded (ST) or fully slatted (FS) buildings from 35 kg to slaughter at 104 kg liveweight. In the ST building, only the straw bedding enriched half of the pens and half received additional enrichment in the form of a single hanging ‘toy’. In the FS house, half of the pens were provided with the same hanging toy, whilst the remaining pens were provided with four such toys. Time spent in toy manipulation was <2% in both housing systems, and did not differ in comparison of the same toy in different housing systems, or the different numbers of the toy per pen within the FS house. Manipulation of straw bedding occupied a much higher proportion of time (21%). In the absence of straw, significantly more investigatory behaviours were directed towards pen components, with a similar tendency in behaviours directed at pen-mates. It was concluded that environmental enrichment in the form of a hanging toy failed to provide the same level of occupation as seen with straw bedding. Since the ratio of pigs to enrichment object had no effect on the level of enrichment manipulation, or on pig or pen-directed behaviours, this difference cannot be attributed to spatial limitation. Functional enrichment should occupy animals to a great extent to prevent them from performing adverse behaviours; therefore the reasons behind the difference in occupation time between straw manipulation and enrichment object interaction require further investigation.