This qualitative study explored the concept of acceptance of wholegrain foods in an adult population in the UK. Data was generated via focus groups with volunteers from a randomised controlled wholegrain based dietary intervention study (the WHOLEheart study). WHOLEheart volunteers, who did not habitually eat wholegrain foods, were randomised to one of three experimental regimes: (1) incorporating 60. g/day whole grains into the diet for 16. weeks; (2) incorporating 60. g/day whole grains into the diet for 8. weeks, doubling to 120. g/day for the following 8. weeks; (3) a control group. Focus groups to examine factors relating to whole grain acceptability were held one month post-intervention. For participants incorporating whole grains into their diet, acceptance was dependent upon: (a) 'trial acceptance', relating to the taste, preparation and perceived impact of the wholegrain foods on wellbeing, and (b) 'dietary acceptance' which involved the compatibility and substitutability of whole grains with existing ingredients and meal patterns. Barriers to sustained intake included family taste preferences, cooking skills, price and availability of wholegrain foods. Although LDL lowering benefits of eating whole grains provided the impetus for the WHOLEheart study, participants' self-reported benefits of eating wholegrain foods included perceived naturalness, high fibre content, superior taste, improved satiety and increased energy levels provided a stronger rationale for eating whole grains.