Abstract: A needle guide assembly for inserting a needle into the body of a patient in order to access a subcutaneous target, such as a vessel, is disclosed. In one embodiment, the needle guide assembly comprises a needle guide body that is configured to at least indirectly and removably attach to an image producing device, such as an ultrasound probe. The needle guide body defines at least first and second elongate guide channels. Each guide channel defines a unique insertion angle with respect to a longitudinal axis of the ultrasound probe. Further, each guide channel is configured to accept needles of differing gauges. In other embodiments other needle guide assemblies are disclosed that include multiple guide channels for inserting a needle at a variety of insertion angles into the patient's body. Related methods are also disclosed. In yet other embodiments, needle guide assemblies including needle stop features are disclosed.