This essay reviews a huge body of literature on the study of the conversational phenomenon of overlap, revealing a wide diversity of scholarly interests in various facets of the phenomenon. The essay mainly addresses characterisations and classifications of overlap, besides a cross-cultural study and the gender-differentiated use of overlap. A number of researchers have resorted, in their classification of overlap and interruption, to either the semantic content of the second speaker’s utterance with respect to that of the first speaker, or the pragmatic functions of overlap or both. Most of these researchers have used the semantic and/or pragmatic classification not in replacement for but as an addition to a structural one. As work on overlap in the conversation analytic perspective is increasingly being refined, similar work in the area is expected to spill over to the analysis of conversations in languages other than English, specifically with respect to issues of overlap onset, resolution and retrieval. With the advent of more advanced video and computer technologies, the conversation analysis of overlap will increasingly be multimodal, incorporating the various nonverbal and prosodic cues accompanying the occurrence of overlaps during the course of a conversation. Overlap studies in the relatively untapped new communication media such as Instant Messaging and other online chatting programs may also begin to emerge. In the quantitative study of overlaps, cross-cultural and cross-gender studies will continue to expand, especially with the increasing availability of various properly transcribed conversational corpora; studies of this conversational phenomenon in different socio-cultural contexts are also expected. But to study overlaps in the quantitative mode, a more refined system of classification which takes into consideration conversation analytic accounts of overlap occurrences will probably be needed. In addition, assigning social, moral and/or cultural values to the occurrence of overlap in a conversation may also need to be more cautious.