Normal small bowel biopsy followed by coeliac disease. We report four patients (two children, one adolescent, and one adult) having normal small bowel mucosa shown on a biopsy specimen taken before the initial diagnosis of coeliac disease was made. The first biopsy was undertaken in two cases because of suspected malabsorption, in the third because of suspected dermatitis herpetiformis, and in the fourth as part of a coeliac disease family study. After a further 2.6 to 9 years on a diet containing gluten, small bowel villous atrophy with crypt hyperplasia compatible with coeliac disease was found on a second biopsy specimen. The HLA type of the patients was that typical for coeliac disease; all were DR3 positive. Within the families three other patients with coeliac disease have been diagnosed, two earlier and one at the time the first biopsy was undertaken. Four other HLA-DR3 positive haploidentical first degree relatives were found and had biopsies. All four had normal small bowel villous architecture, one had an increased intraepithelial cell count, and another was positive for reticulin and endomysium antibodies. Coeliac disease may exist latent in patients having normal mucosa when eating a normal diet containing gluten. 