The prelearning strategy involves activities aimed at students’ preparation in advance of class. The aim of this doctoral thesis was to explore the use of prelearning materials in the secondary chemistry teaching in order to determine the effective way of their design and implementation in real teaching situations. The purpose of the first part of the study was to research the situation in secondary schools with regard to the frequency of using various prelearning activities in chemistry classes and at the same time to explore the influence of demographic characteristics on the use of prelearning activities within the chemistry teacher population. Within the frame of the quantitative descriptive survey research, a self-administered online questionnaire was completed by chemistry teachers from all regions in Croatia. The focus of the second part of the study was on a quasi-experimental research of the use of online chemistry prelearning materials to determine how they affect high-school students' knowledge acquisition of chemistry and its retention. It was found that chemistry teachers most commonly use oral repetition activities in which they ask students questions to activate their preknowledge and repeat key concepts useful for new teaching material while online discussions to encourage textbook reading in advance of class were represented the least. Demographic characteristics affecting the teachers’ use of prelearning activities in chemistry classes were their gender and age. The teachers’ education, teaching subjects, school types and teaching experience were nonsignificant characteristics. In the second part of the study, a statistically significant difference to the benefit of the experimental group on the posttest and retention test indicated a positive effect of the prelearning materials use on students’ knowledge acquisition and its retention in the example of alkane and cycloalkane teaching materials. The students accepted the prelearning materials well and found them useful in preparation in advance of class.