To improve compliance with a gluten-free diet in coeliac disease a simple prototype test kit was developed to detect gluten in foods for use at home. The test is based on monoclonal antibodies to heat-stable gluten proteins which crossreact appropriately with barley and rye proteins. It is suitable for use with a wide range of raw or cooked foods. The food is extracted with dilute hydrochloric acid and 1 drop of the extract transferred to an antibody-coated tube; enzyme-labelled gluten detection antibody is added and after 3 min the tube is washed and colour developer is added. The reaction is stopped after 2 min, stabilising the blue colour. The home kit was compared with a quantitative laboratory kit, and the qualitative agreement was very good. The kit could distinguish foods with trace gluten contents (acceptable for a "gluten-free" diet) from those with a slightly higher but unacceptable gluten content. In a trial of the prototype kit by 47 coeliac disease patients of diverse ages and educational backgrounds, 93% of tests correctly identified foods as acceptable or unacceptable.