There has been a tremendous increase in the usage of multimedia services with the rapid penetration of mobile devices. In parallel to the technological developments in hardware and software of communication devices, users demand to have higher quality and more reliable services. The developments in network technologies are towards forming a converged structure that mobile, fixed and internet access technologies are able to operate together. Heterogeneous wireless networks have a critical role in order to meet dramatically increasing traffic demand. As a result of better operation of the systems with the help of heterogeneous wireless networks, it is possible to serve subscribers with higher performance with the help of offloading which transfer the traffic load from a network to another one. Various strategies are used in order to offload traffic between different wireless communication technologies. The main objective of this thesis is to examine offloading strategies which provides operation of different wireless communication technologies efficiently in heterogeneous wireless networks. The performance evaluations of different offloading strategies in various scenarios are implemented. The comparisons of strategies which are user initiated and network initiated are provided by considering their overhead load.