Qualitative methodology is extensively used in a wide range of scientific areas, such as Sociology and Psychology, and it is been used to study individual and household decision making processes. However, in the Transportation Planning and Engineering domain it is still infrequent to find in the travel behavior literature studies using qualitative techniques to explore activity-travel decisions. The aim of this paper is first, to provide an overview of the types of qualitative techniques available and to explore how to correctly implement them. Secondly, to highlight the special characteristics of qualitative methods that make them appropriate to study activity-travel decision processes. Far from been an unempirical or intuitive methodology, using qualitative methods properly implies a strong foundation on theoretical frameworks, a careful design of data collection and a deep data analysis. For such a purpose, a review of the scarce activity-travel behavior literature using qualitative methods, or a combination of qualitative and quantitative approaches, is presented. The use of qualitative techniques can play a role of being a supplementary way of obtaining information related to activity-travel decisions which otherwise it would be extremely difficult to find. This work ends with some conclusions about how qualitative research could help in making progress on activity-travel behavior studies.DOI: http://dx.doi.org/10.4995/CIT2016.2016.4268