Structures having a plurality of discrete insulated elongated electrical conductors projecting from a support surface which are useful as probes for testing of electrical interconnections to electronic devices, such as integrated circuit devices and other electronic components and particularly for testing of integrated circuit devices with rigid interconnection pads and multi-chip module packages with high density interconnection pads and the apparatus for use thereof and to methods of fabrication thereof. Coaxial probe structures are fabricated by the methods described providing a high density coaxial probe.