The bioartificial (hybrid) pancreas separates transplanted tissue (i.e. islets of Langerhans) from the diabetic host and thus protects it against immune rejection. The membranes employed in such devices must be impermeable for immunocytes and immunoglobulins but--due to the particular construction of the devices--more or less selectively permeable for glucose and insulin. A short survey is presented on different systems from the viewpoint of the transport functions realized, i.e. diffusion systems, ultrafiltration systems, and combined diffusion-ultrafiltration systems. All these devices are still in a developmental stage.