Results showed significant modification of perceived bitterness in beer by hop aroma depending on the inherent level of bitterness. These modifications were mainly driven by olfaction – in an example of taste-aroma interactions, as well ascertain tactile sensations elicited by the hop aroma extract in the oral cavity. At low bitterness, beers with hoparoma added were perceived as more bitter, and of ‘rounded’ bitterness character relative to those withouthop aroma. When judges used nose clips, this effect was completely eliminated but the sample was perceivedto have a ‘harsh’ bitterness character. Conversely, at high bitterness, even when nose clips were used, judgesstill perceived beers containing hop aroma to be more bitter. These increases in bitterness perception withnose clips indicates the stimulating of other receptors, e.g. trigeminal receptors by hop aroma extract, which intandem with the high bitterness, cause perceptual interactions enhancing bitterness intensity and also affectingbitterness character. Bitterness character attributes such as ‘round’ and ‘harsh’ were found to significantly dependon bitterness and aroma levels, with the second level of aroma addition (245 mg/L) giving a ‘rounded’ bitternessin low bitterness beers but ‘harsh’ bitterness in high bitterness beers. The impact of aroma on temporal bitternesswas also confirmed with time-intensity measurements, and found to be mostly significant at the highest level ofhop aroma addition (490 mg/L) in low bitterness beers. These findings represent a significant step forward interms of understanding bitterness flavour perception and the wider impact of hop compounds on sensoryperception.