In this chapter, we first present the extent of cross-linguistic differences in the uses of discourse connectives and relations, and discuss their implications for theories of discourse. We make a distinction between discourse relations, that seem to exist in all languages and their mapping onto specific connectives that is most of the time language-specific. We also present the kind of data that can be used to perform contrastive studies, emphasizing their advantages and limitations. Connectives are also used quite differently across different genres within the same language. These differences are particularly evident between spoken and written genres. We present the variations linked to genres in this chapter, and underline the necessity to develop more cross-linguistic studies that are also varied in terms of genres. Results from corpus studies comparing languages or genres have increasingly been used as input for experimental research. We discuss in particular how observations about connective usage across genres has been important for studies analyzing discourse processing, as well as first and second language acquisition