Very High Energy Cosmic Rays

In these lectures I review a number of issues in relation to ultra high energy cosmic rays and prospects for their detection with particular emphasis on recent developments in the study of cosmic rays detected at high zenith angles. The first part is an overview of the field and the second part an outlook. Finally a section is devoted to addressing the radio technique. The recent confirmation of the Askar'yan effect at SLAC has renewed the interest in the potential of detecting the emission of coherent radio pulses from showers developing in dense media. (Author)