The International Adult Literacy Survey (IALS), an initiative of the Organization for Economic Cooperation and Development (OECD), was carried out in the early to mid-1990s across more than 20 countries. It was followed in the early years of the 21st century by the Adult Literacy and Life Skills (ALL) survey and the Programme for the International Assessment of Adult Competencies (PIAAC, currently in data analysis). This article reviews the philosophical basis, theoretical underpinnings and data analysis of the original and subsequent IALS-based surveys. The purpose is to inform users of the survey data of what the surveys can, and cannot, provide. The author argues that the key use of these surveys is providing insights into population-level distribution of one form of literacy, namely a particular kind of text consumption in a developed society. He also points out the challenges regarding the use of the survey series for making international comparisons, for documenting change over time and for representing broad models of literacy. The tendency to use the survey findings for these uses is considered by the author as a misuse of the data, which leaves the potential of the IALS surveys to provide insights into the effectiveness and equity of different educational systems largely untapped.