Sign language typology is the study of languages that use the visual-gestural rather than the auditory-vocal modality, and allows typologists to consider issues of language modality alongside typological patterns. Modality effects may be absolute, where features exist only in one of the modalities, or relative, where features are more frequent in one modality than the other. Sign language typologists, while widening the scope of typological investigations, are also concerned with many of the same issues as spoken language typologists, such as areal typology, grammaticalisation, and methodological questions. Although sign language typology is one of the more recent areas to emerge in the field, several studies have examined domains of linguistic structures in over 30 sign languages, and we focus on key findings from research in the domains of interrogatives, negation, possession, and numerals. The aim of the chapter is not to give comprehensive overviews of each domain, but rather to highlight issues of general relevance. We conclude with reflections on the emerging field of cross-modal typology, where data from spoken and signed languages are systematically included. This endeavour may necessitate the redefinition of terms and concepts, and will present new challenges for spoken and sign language typologists alike.