A device (10, 110) for facilitating insertion of a needle or a cannula into a vein of a patient, the device (10, 110) comprising means (20, 120, 220) for creating a localized area of reduced pressure at a surface of the patient's skin, so as to facilitate expansion of an underlying part of the vein, and means (26, 226) for enabling insertion of a needle or cannula into the expanded part of the vein.