People with dementia and carers may be vulnerable to loneliness and isolation. The IDEAL study includes two loneliness measures: 6 item de Jong Gierveld (DJG) scale (range 0-6) and a single-item self-report measure and the six-item Lubben social network scale (range 0-30). Full data are available for 1533 people with dementia for self-rated loneliness and for 1455 for the DJG scale and 1232 and 1195 carers respectively. For isolation complete data are available for 1489 people with dementia and 1252 carers. The prevalence of severe loneliness for people with dementia were 10% (self-rated) and 5% (DJG score 5+), approximately the population norm, and 15% and 18% respectively for carers. Most people with dementia or carers did not rate themselves as lonely ((79% and 71%) compared with 65% and 39% using the DJG scale. One third, 35%, of people with dementia were at risk of isolation compared with 18% of carers.