Data from 80 junior high school students who completed the Assessment of Language and Reading Maturity (ALARM) test battery were used to delineate elements within the concept of mature reading comprehension. Stepwise multiple regression analyses were performed on the 15 ALARM test factors to isolate both the principal elements and the "trace elements" (overlooked factors/key relationships that nourish reading comprehension to mature levels) of mature reading comprehension. The principal elements in both mature reading comprehension and conventional reading comprehension were found to be abstract verbal reasoning, critical judgments-useful information, and critical judgments-reasonability. Of the five trace elements isolated, cultural/experiential compatibility, elaborative thinking, and general knowledge were concluded to be the most important of mature reading comprehension in junior high school students. The isolation of these trace elements was seen as a benchmark in the study of reading maturity, because the elements may have profound implications for indepth reading diagnosis and the selection of reading methodologies. (RL)