Abstract: A catheter (2) is used in medical applications, for example for the retrieval of a sample from a patient or the insertion or retrieval of medical devices such as filters, stents (3) to and from the patient. The catheter (2) includes an expandable tip (6) at a leading portion of a catheter tube portion (5). This expandable tip (6) can retrieve or deliver samples, medical devices, etc. (3), which are slightly larger than the dimensions of a main catheter tube (5) inserted into the patient. The expandable tip (6) can also include extension members (10) which provide axial support to the expandable tip (6) but which still allow expansion in the radial direction.