Abstract: A coupling device (3,4) for medical purposes with at least one coupling channel (9,18) having a mouth in a coupling surface (10), for sealed co-operation with at least one access channel (7) with a mouth in a connecting surface (?). of an access device (2), which is connectable to a patient, is distinguished in that the coupling surface (10) includes a flexible portion (11) for contacting against the connecting surface (6) and being of a material having a higher degree of flex than a primary material of the coupling device, which portion for sealing purposes surrounds the mouth of said at least one coupling channel (9,18).