This study explored the enhancement of comprehension of expository text by three specific types of embedded explication--etymological, causal, and analogical--together with momentum effects from sequencing. Four factors were examined: (1) the experimental effects of presenting the section of the script containing explications of new terms before the new concepts; (2) the effects of etymological explications on acquisition of the meaning of new terms; (3) the effects of explication of causal relations on construction and retrieval of information; and (4) the effects of analogical explication on integration of information in long-term memory. Instructional materials were developed which presented new vocabulary before new facts or new facts before new vocabulary. For each sequence, one control group received filler material and three groups received different types of explication. Subjects were 184 undergraduate students enrolled in elementary science education courses, and the instructional content consisted of a an 1,800 word instructional unit on the human heart. On the first day of the study, students were given 15 minutes to read the scripts. Two days later they received the test packet, which included a 5-minute drawing test. Overall, the effects of explication were significant on the drawing and terminology tests, while the effects of vocabulary sequence were significant only on the drawing test. It is concluded that, in order to be effective, text-based explication must target mental processes, and that, in cases where the information is conceptually dense, embedded explication can both relieve density and enhance processing. (4 tables, 29 references) (BBM)