Abstract: A reagent supply system for a medical anlytical instrument includes a reagent space provided on the instrument and reagent vessels which are received in the reagent space. In the reagent space there is provided at least one reagent vessel compartment with a bottom, lateral guide elements, and a top guiding element, as well as a front stop. The instrument contains a fluid communication system for connection with a reagent vessel situated in the reagent vessel compartment. On the end face of the reagent vessel compartment is disposed a hollow needle near the bottom surface thereof and extending in a direction which is parallel to the bottom surface. The reagent vessel has on its front wall facing the end face a pierceable seal with a pierceable elastic stopper.