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The ever-increasing application of computer and internet mandates a longer domain for computer-mediated-communication (CMC). Internet chat as a principal feature of CMC has attracted tremendous attention among the youths in recent years.  Thus, this study has focused on the written chats of 100 Iranian university students majoring in different disciplines. We analyzed 400 chat samples (composed of 4000 moves) in terms of opening and continuing speech functions based on Eggins and Slade’s (1997) model of casual conversation. We also examined humor and paralinguistic features based on taxonomies of Huffaker and Calvert (2005) and Nastri, Peña, and Hancock (2006). Among the various types of speech functions, nine opening speech functions, seven continuing speech functions and four humor and paralinguistic features were investigated. The analysis of the data shows that the salient opening speech function has been ‘statement: opinion’ which provides attitudinal and evaluative information. Additionally, the outstanding types of continuing speech functions are ‘prolong: extend’, ‘prolong: enhance’, and ‘append: elaborate’. Therefore, it is in order for the participants to offer additional or contrasting information to the previous move or qualify it by giving details of time, place, condition, etc. Moreover, in case of interruption by the other chatter, the participants mostly tend to clarify, exemplify or reiterate the previous move. Furthermore, the participants produced irony, as a humorous element, in a great volume which is indicative of their tendency toward being indirect during conversation. The subjects also used many paralinguistic features such as misspellings and repeated punctuations in order to express their emotions and attract their partners’ attention in the absence of verbal communication.