This chapter contains sections titled: Historical Background of Schottky Contacts on ZnO Recent Schottky Barrier Studies The Influence of Surface Preparation on Schottky Barriers The Influence of Defects on Schottky Barriers The Influence of ZnO Polarity on Schottky Barriers The Influence of Chemistry Charge Transport and Extended Metal–ZnO Schottky Barriers Conclusion Acknowledgements References