This paper examines the heterogeneities of wireless networks from six different perspectives, namely mobile terminals, radio access technologies (RATs), network services, users, network operators, and network geographical areas. These different aspects of wireless network heterogeneities offer certain benefits but also pose some challenges to effective management of radio resources. The challenges of wireless network heterogeneities are highlighted in this paper and possible solutions are proffered. The paper then compares recent network selection algorithms proposed for wireless networks with respect to the aspects of heterogeneities considered. Comparative analysis of the different network-selection algorithm shows that whereas RAT, services, and users heterogeneities have received much attention in the literature, terminal, operator, and geographical area heterogeneities have not been widely considered. Thus, more attention should be given terminal, operator, and geographical area aspects of wireless network heterogeneities so that the problems of radio resource management in wireless networks can be addressed in a more holistic way. An algorithm that considers the different aspects of network heterogeneities is proposed, and simulation results are given to highlight the effects of network heterogeneities on connection-level quality of service provisioning in heterogeneous wireless networks.