The objective of this book is to help users use WEIRCOME software for designing diversion weir headwork structures covering computation of necessary and related hydrologic, hydraulics and structural aspects. Windows-based and user friendly software named WEIRCOM has been developed in Visual Basic Programming Language for use in the complete design of a diversion weir headwork structure. It deals with the overall required hydrologic, hydraulics and stability computations thereby sizing the dimensions of each of the components of the diversion weir and can finally estimate the total cost of the headwork structure. The software has the capacity of producing self contained structured report in text format for users to save and incorporate it in the final detailed design document. The software has also reasonable access to see the immediately executed results in the interface windows. WEIRCOM have been designed to operate in two modes: - as independent executable file and as installation software package. In both cases, the software can easily be used in both Laptops and desktop computers with windows operating systems.