Abstract: A monitoring device (1) is provided for monitoring the presence of a skin piercing vascular access device, for example a needle (4), the monitoring device comprising: a mount having an ultrasonic transmitter and an ultrasonic receiver therein; attachment means (3) for attaching the mount to a patient adjacent a vascular access point such that, in use, a vascular access device (4) entering the patient at the vascular access point, passes underneath a sensing section of the base; control electronics to monitor the signal received at the receiver, and wherein when the vascular access device is underneath said sensing section, ultrasound produced by said transmitter passes through the patient skin and is reflected by the patients body tissues and by the vascular access device (4), and when the vascular access device (4) is not underneath said sensing section, ultrasound produced by said transmitter passes through the patients skin and is reflected by the patients body tissue only, and wherein the control electron