When conducting qualitative research, scholars should consider the relation between data collection and analysis as well as between theory and data. There are at least two ways to relate data collection to analysis in the research process. In a linear-sequential approach, researchers first collect all data and then start to analyze. This is common in quantitative research but could also be applied in qualitative research, for instance when doing content, thematic, discursive, conversational, or phenomenological analysis after collecting all data. In contrast, an iterative approach refers to an interplay between data collection and analysis. Researchers move back and forth between data collection and analysis during this research process. The ongoing data analysis guides researchers to change or add a new data gathering method, to decide which data to collect next and where to find them. The iterative approach is essential, for example, in ethnography and grounded theory, but could be adopted in a range of qualitative research approaches. The two approaches of how to relate data collection and analysis to each other should be understood as ideal types or the opposite ends of a continuum, in which researchers could be more or less close to one of the ends. Concerning the relation between theory and data, researchers might either use theoretical knowledge to interpret and analyze their data or else try to ignore previous theoretical knowledge to be open to discover patterns, themes, concepts, or theory from data. Once again, these two approaches should be considered as located on a continuum. When it comes to this complex and even contested relation between theory and data, Kelle argues that qualitative researchers have to deal with two conflicting challenges: (a) the general accepted epistemological tenet that empirical research must always refer to previous insights and already existing knowledge; and (b) that social life and its meanings, actions and structures are constantly changed and reinvented, and therefore, the researchers have to be open to explore the unknown and unpredictable at the same time as being aware that such an openness may be hampered by theoretical preconceptions researchers carry with them. The relation between data collection and analysis and between theory and data can be discussed in terms of deduction, induction, and abduction, which is the aim of the current chapter. Because deduction and induction have often been discussed in the social research literature, we focus in particular on abductive reasoning and its potential role in the relation between data collection and analysis and between theory and data in qualitative research.