Letter-sound knowledge is necessary for children to begin reading and writing, and kindergarteners who know only a few letter sounds are at risk for later reading difficulties. This study examines the letter -sound knowledge of 1197 first-time kindergarteners who were economically disadvantaged, in light of six hypotheses about letter-sound knowledge acquisition: (1) the letter-name structure effect hypothesis, (2) the letter-sound ambiguity hypothesis, (3) the letter-name knowledge hypothesis, (4) the own-name advantage hypothesis, and 5) the phonological awareness facilitation hypothesis, as well as the (6) interactions between phonological awareness and letter-name structure. Results using three-level multilevel modeling indicate that letter sounds have varying levels of difficulty and several letter- and child-related factors are associated with naming a letter sound correctly. Implications for instruction are discussed. (author abstract)