To investigate the relationships between content structure of prose and information processing abilities, one group of 61 college students read passages with lots of words explicitly describing conjunctive relations among sentences and some other 61 students read passages with few such words. A memory test, a vocabulary test and an inference test were administered to measure the relevant abilities. An immediate cued recall, a delayed cued recall and a delayed free recall were measured as dependent variables. Results strongly suggest the existence of a disordinal interaction between passage type and inference ability. That is, a number of connectives stating explicitly conjunctive relations among sentences influenced the understanding and retention of content differentially according to the reader's inference ability. Implications of this aptitude-treatment interaction to education were discussed.