In the most recent assessment by the Programme for the International Assessment of Adult Competencies (PIAAC), approximately 19% of adults in the United States scored at or below Level 1 in literacy (National Center for Education Statistics [NCES], 2019a). Adults who performed at Level 1 were only able to identify one key piece of information from short real-world texts, and adults who scored below Level 1 struggled with this basic task. Because the PIAAC is based on a nationally representative sample, this grim finding suggests that almost one in five adults have difficulty understanding everyday texts, which include key documents like workplace memos, medical forms, and notices from children's schools. Thus, these adults' low reading skills impede their functionality in today's information-driven society. In addition to gathering data on the U.S. household population, the PIAAC Survey of Incarcerated Adults was conducted during the 2014 National Supplement phase of data collection to provide information on this particularly vulnerable segment of adults (Rampey et al., 2016). The purpose of the present study was to examine potential differences between low-skilled incarcerated adults and their counterparts in the general U.S. household sample who completed the Reading Components Supplement based on individual characteristics reported by PIAAC test-takers on the background questionnaire. Thus, the primary research questions were: Are demographic characteristics (i.e., age, race/ethnicity, educational attainment, self-reported learning disability (LD) status, native language status, overall health, and parental education levels) related to the literacy performance of low-skilled adults (U.S. household and prison sample)? Do the relationships of demographics to literacy performance vary based on sample type (U.S. household vs. prison sample)? Given the exploratory and novel nature of directly comparing these two samples, the study did not make specific hypotheses about each demographic category in relation to literacy performance, but instead selected these demographics based on the heterogeneity of the samples included.