The term data warehouse was first used by Inmon in 1990 which he defined as “A warehouse is a subject oriented, integrated, time-invariant and nonvolatile collection of data in support of management decision making process” [Inmon, 1990]. On the other hand, Ralph Kimball provided a much simpler definition of the data warehouse. In the book ‘The Data Warehouse Toolkit’ he said that a data warehouse is “a copy of transaction data specifically structured for query and analysis” [Inmon and Kimball, 1996]. This paper provides theoretical description of data ware housing. Implementation of clinical Data warehousing were analyzed, finally evaluating them. The proto type considered for implementation has been collected from the East Hospital London Clinical Data Warehouse Project.