Theoretical saturation of data is a term in qualitative research, mostly used in the grounded theory approach. Theoretical saturation of data means that researchers reach a point in their analysis of data that sampling more data will not lead to more information related to their research questions.(1) No additional data can be found to develop new properties of categories and the relationships between the categories are disentangled. Researchers see in their data similar instances over and over again and that make them empirically confident that their categories are saturated, the descriptions of these categories are thick and a theory can emerge. Researchers are allowed to stop sampling data and to round off their analysis.

Explicit guidelines for determining theoretical saturation are lacking and therefore researchers have to support their claims of saturation by an explanation of how they achieved saturation including clear evidence.(2) The application of the term saturation beyond the grounded theory approach is a topic of debate.(3)

(1) Seale C. Grounding theory. In: Seale C, editor. The Quality of Qualitative Research.London: SAGE Publications Ltd; 1999. p. 87-105.

(2) Bowen GA. Naturalistic inquiry and the saturation concept: a research note. Qualitative Research 2008;8(1):137-52.

(3) O’Reilly M, Parker N. ‘Unsatisfactory Saturation’: a critical exploration of the notion of saturated sample sizes in qualitative research. Qualitative Research 2013;13(2):190-7.