Interference in wireless communication systems is generally thought of as being produced by an outside, uncontrolled source. With this philosophy, interference must be accounted for and its detrimental effects mitigated. However, there are also cases where interference can be leveraged during system design for its own purpose. This presentation discusses tools for interference design, and proposes new methods for using intentional interference in wireless communications. First, we introduce two tools that can be used during design to help select system parameters and reduce the computational complexity of system analysis. We then present two examples of methods of interference design in wireless communication systems. The first method eliminates inter-system interference and processing redundancies in a jointly-designed wireless communication and radar systems. The second method concerns secret communication, where it is shown that clever design of interference can simultaneously reduce power expenditure and increase secure communication rates. ; Ph.D.