It is a basic insight of CA that participants orient to temporality for producing and understanding action in interaction (Schegloff 2007). CA has shown that sequential organization is constitutive of the fundamental context-sensitive and context-renewing properties of turns (Heritage 1984). Building on early work by Goodwin (1979), researchers have increasingly zoomed in on the fine-grained organization of reciprocal microsequential relationships between actions, responses and responses to responses within the scope of single actions in the making (Mondada 2018; Mondada & Deppermann submitted). Yet, recent research on longitudinal CA (Pekarek Doehler et al. 2018; Pekarek Doehler & Deppermann 2021) has shown that not only temporal relationships below, but also above the level of sequences matter to interactional practices. 
In this paper, I will deal with an interactional order that operates across sequences: interactional histories. Interactional histories emerge over a series of encounters including the same participants. Interactional histories are crucial for many activity types, e.g., aiming at psychological change (psychotherapy: Voutilainen et al. 2011), developing skills and knowledge (pedagogical settings: Deppermann 2018), or getting acquainted (D’Antoni & De Stefani 2022). During these encounters, participants establish common ground, develop shared routines, and arrive at increasingly economic ways of referring and accomplishing joint tasks (Deppermann & Schmidt 2021; Deppermann 2024). This is the progressive dimension of interactional histories. At the same time, interactional histories have a retrospective dimension (Deppermann & Haddington 2026). Participants reflexively index, and sometimes explicitly refer to, their interactional histories by the ways in which they accomplish sequential actions. This is done by recipient-designed action formation, the choice of referential expressions, and presuppositions, but also by phenomena such as quoting, humor, innuendo, or irony. 
In my talk, I will discuss the specific requirements for studying interactional histories within the methodological framework of CA, give an overview over studies on interactional histories, give examples of trajectories of and changes over interactional histories in various activities, and show how interactional history is reflexively indexed in situated actions. Epistemologically, I will argue that memory and common ground are fundamental determinants of interactional conduct, whose relevance as a participant’s concern may be accessed in the methodological framework  of CA by analyzing interactional histories.