No accurate figures exist as to how many people in Australia have IBD, but it is estimated that there are possibly 30,000 people with Crohn's and a similar or lesser figure for ulcerative colitis.

In recent years there appears to have been a dramatic rise in the number of people with Crohn's disease, whereas ulcerative colitis seems to have levelled out.

The most common age groups to be diagnosed with Crohn's disease and ulcerative colitis are those in their teens and twenties, followed by those in their forties and fifties, although people of all ages are diagnosed, including young children and the elderly.