OBJECTIVES: Rheumatoid arthritis (RA), psoriasis (PS), Crohn's disease (CD) and ulcerative colitis (UC) are autoimmune related diseases. The purpose of this study was to estimate the mortality rate of patients for each of these four conditions, relative to the overall population, adjusting for age and sex differences of the each patient group. METHODS: The analysis was based on the THIN database for 2004. This data source is based on the registration in GP-practices for a 4% representative sample of the overall UK population. From the overall-population sample (n= 2.278.100), patients were identified based on the READ codes for each of these conditions in the previous 4 years. A subgroup of severe cases was identified, based on previous drug treatment. The standardised mortality ratio (SMR), defined as the proportion of the observed number of deaths and the expected number, based on the age and gender specific mortality rates for the overall population, was calculated for each patient group. 95% confidence intervals were calculated. RESULTS: 2% of the studied population suffers from one or more of the four diseases : RA ( 0.44%), PS (1.3%), CD (0.14%) or UC (0.16%). The SMR for all four disease conditions combined was significantly higher (132 [122,143]) compared to the global UK population. Within the four groups, RA (158 [139,179]), CD (165 [108,241]) and PS (116 [103,130]) all showed statistically increased mortality. The SMR was (ns) higher for UC (122, [89, 163]). Within each of these disease groups, mortality was higher for severe patients, but did not reach statistical significance, possibly due to the relatively small sample size of these subgroups. CONCLUSION: Patients suffering from Crohn's disease and rheumatoid arthritis have a 60% increased mortality compared to the overall UK population. Mortality is about 20% higher for patients with psoriasis and ulcerative colitis.