Following the discourse model of coherence relations (Hobbs 1983; Redeker 1990, 1991; Sanders et al. 1992), the current study examines different functions of o sea at the pragmatic and textual levels of discourse. O sea is analyzed as a discourse functional unit (DFU) as realized in three utterance positions: initial, medial, and final. This study examines the frequency, distribution, and discourse functions of the DFU o sea in conversational Spanish as realized in three coherence relations: semantic, pragmatic, and textual. The examples of o sea analyzed are taken from natural conversations recorded in central Mexico and from El Habla de Monterrey corpus. The study finds that the pragmatic function was the most common and this function included the use of o sea as a marker to signal a conclusion or explanation, or in its epistemic function. The textual function of o sea was the second most frequent and was used to restart or reorient discourse, as an intensifier or continuer in conversation, or to offer the floor.