HELLP syndrome (haemolysis, elevated liver function tests and low platelets) is a multiorganic disease and has been described in combination with pre-eclampsia/eclampsia, but even without symptoms of gestosis. There are signs, that HELLP syndrome represents an "acute status of autoimmunity". Since immune mechanisms play a fundamental role together with other factors in the development of type I diabetes mellitus, a combination of autoimmune reactions could explain the development of type I diabetes during an altered immune status. We report on the course of a pregnancy complicated by HELLP syndrome, which developed type I diabetes mellitus in the same pregnancy. A subsequent pregnancy with adequate diabetes therapy was uncomplicated and without recurrence of HELLP syndrome.