A major challenge in research with struggling adult readers is their heterogeneity in reading-related competencies and demographic characteristics. The purpose of this investigation was to identify unique profiles of skill sets among struggling adult readers and explore informative demographic differences between profiles. Using latent class analysis with a sample of 542 struggling adult readers, we uncovered four empirically distinct classes of readers based on their performance on ten assessments of lower-level and higher-level competencies. On all measured competencies, globally impaired readers (n = 123) demonstrated the largest deficits and globally better readers (n = 86) outperformed all other classes. Two intermediate profiles, weak decoders (n = 144) and weak language comprehenders (n = 189), exhibited complementary patterns of strengths and weaknesses on lower-level and higher-level competencies. One-way ANOVA and chi-square tests of difference indicated that the classes differed significantly in terms of reading comprehension performance, age, and language background but not high school completion. Implications for instruction and future research are discussed. [For the Grantee Submission, see ED604269.]