The effects of interest level on comprehension and word-recognition instructional levels were investigated in samples of fifth- and sixth-grade pupils. The effects of sex, ability, interest, and type of skill on performance on informal reading inventories were tested using a four-factor analysis of variance; each grade level was examined separately. Significant main effects were found for ability and type of skill at both the fifth- and sixth-grade levels and for interest at the sixth-grade level. The interaction of sex and type of skill was also significant. Conclusions of the study were that high-interest content had a greater effect on comprehension than on word recognition, increased the instructional levels of males more than of females, and had a greater effect on average and below-average readers than on above-average readers. (Author/AA)