A two-part opinionaire was used to identify teachers' perceptions of the SCIS-II elementary science program. Of particular interest were perceived barriers to effective implementation of the program. The first part of the opinionaire was administered to 685 individuals, or 96.8% of the elementary teachers in a metropolitan school district. The second part was completed by a group of teachers at each grade level in each of the 31 elementary schools, with completion rates ranging from 77%–97% for the 13 SCIS-II units. Results indicate that grades K-2 teachers rated the program more positively than grades 3–6 teachers; teachers who rated the program highly perceived fewer barriers to effectively utilizing the program; and teachers rated the program higher for developing social skills and positive attitudes than for teaching science content and processes. Data on problems with individual SCIS-II units indicated that the viability and performance of the living organisms are problematic in all life science units. Further, the small number of insightful evaluative comments received for the last one-third to one-half of some units suggests that a significant portion of teachers are quitting the units before reaching the end.