Students have conceptions about the relationship between instructional interventions and learning or, in other words, students have 'instructional metacognitive knowledge'. In this study, the efficiency of instructional interventions has been investigated as a specific object of students' instructional metacognitive knowledge. By means of a survey, conceptions about the efficiency of various instructional interventions of 488 freshmen in educational sciences and psychology have been investigated. Two research questions directed this exploratory study: (1) How do students assess the efficiency of instructional interventions; and (2) Do differences in gender, educational background, and/or subject of study affect evaluations of the efficiency of instructional interventions. Results show that respondents regard regular instructional interventions at the university directed toward, or supporting, surface-level processing and reproduction to be highly efficient. The use of technology is conceived as inefficient by these students. The limited number of differences between groups of students also suggests students' conceptions to be both consistent and robust.