The use of holograms and other diffractive optically variable devices have been used successfully in the fight against counterfeiting of security documents for several years. More recently they have become globally accepted as a key security feature on banknotes as reflected in their prime use on the Euronotes to be issues in 2002. The success of the design and origination of these images depends upon their strong visual appeal, their overt and covert content and the ability to offer unique features that provides an extremely difficult barrier for the would be counterfeiter to overcome. The basic design principles both for banknote and general security print application are discussed in this review document. TO be effective as a security device the image must be fit for the purpose. This means that the image must contain the level of overt and covert features that are easy to recognize, containing high level security features and form part of an educational program aimed at the product user and specifically trained security personnel. More specifically it must meet a clearly defined performance criteria.