With the completion of first draft of human genome in 2001, predictive diagnostic procedures that involves testing individuals for a number of specific genetic variations that indicate whether they are predisposed to a disease, whether the progression of the disease can be slowed by therapies or life style changes or whether a specific therapy will be effective are being carried out. The main limiting factor is the collection of sufficient genetic data to gauge important variations within individuals and how these variations relate to disease predisposition or the reaction to particular medicine. This article relates to various issues that need to be overcome relating to collection, analysis and accurate predictions that can be made from genomic information.