OBJECTIVE: Case reports have indicated a link between coeliac disease (CD) and immune thrombocytopenic purpura (ITP). Two national, register-based studies were carried out to investigate a possible association between CD and ITP and vice versa. MATERIAL AND METHODS: In a cohort study of 14,347 individuals with inpatient diagnoses of CD and 69,967 reference individuals matched for age, gender, calendar year and county, the Cox regression was used to estimate the risk of subsequent inpatient diagnoses of ITP (of any type or chronic). In a case control design, conditional logistic regression was used to assess the risk of exposure (diagnosis of ITP prior to CD) in 15,382 cases (individuals with diagnoses of CD) and 76,824 matched controls. Diagnoses of CD and ITP were identified through the Swedish National Inpatient Register. RESULTS: Individuals with CD were at increased risk of both subsequent ITP of any type (hazard ratio (HR)=1.91; 95% CI=1.19-3.11; p=0.008) and subsequent chronic ITP (HR 2.77; 95% CI=1.09-7.04; p=0.033). Risk estimates were similar when reference individuals were restricted to inpatients. There was also a positive association between CD and prior ITP of any type (odds ratio (OR)=2.96; 95% CI=1.60-5.50; p=0.001) or with prior chronic ITP (OR=6.00; 95% CI=1.83-19.66; p=0.003). CONCLUSIONS: We found a positive association between CD and both ITP of any type and chronic ITP, irrespective of which disease came first, and suggest there should be increased awareness of CD in patients with ITP