Online homework systems have been shown to help student achievement in chemistry courses. This study sought to compare the levels of knowledge retention in students over the course of a semester, using two different types of homework systems--the adaptive-responsive system and the traditional-responsive system. Two sections of a first semester general chemistry course were investigated, with one section using the adaptive-responsive system and the other using the traditional-responsive system. Students' grades on cumulative exams were compared across both sections, and it was found that students using the adaptive-responsive system scored significantly higher on the exams and retained significantly more information than the students in the other section. The results of this study should help inform the choices educators make regarding the homework system they choose to use, or even which parts of the different systems they choose to use or not to use based on the outcomes they would like for their student population.