Celiac disease (CD) is an autoimmune enteropathy triggered by the ingestion of gluten in susceptible individuals, and is one of the most frequent genetically based diseases, with a prevalence of 1:200 in the general population. The association between CD and connective tissue diseases (CTD) and autoimmune diseases of the digestive tract (DT) has been described in several case reports but in few extensive studies, with varying prevalence. A high rate of false positive results were observed when low specific tests, such as the anti-gliadin and the guinea pig tissue transglutaminase (tTG) antibody assays were used. In a study of 400 patients with CTD and 218 with autoimmune DT disease, tested for IgA and IgG anti-tTG using the more specific human recombinant antigen, 12 cases (1.9%) of anti-tTG antibody positivity were found, but only 2 (0.3%) were confirmed as affected by CD following small bowel biopsy. Most of the patients testing false positive had primary biliary cirrhosis. In this short review we describe the association between CD and CTD, inflammatory bowel disease and primary biliary cirrhosis, with special emphasis on the diagnostic accuracy of CD antibody assays.