The concept of substance is considered fundamental in order to understand chemistry and other related concepts, but many problems have been reported about its learning process. Considering the importance of textbooks in the training of chemistry teachers, this study aimed to identify the concepts of substance in general chemistry textbook glossaries. In addition, the study assessed the concepts of substance in relation to other chemical concepts and, when available, compared them with the concepts established by the IUPAC. The methodology employed (...) was content analysis and the results showed that concepts and statements related to the term ‘substance’ are different in the general chemistry textbooks analyzed. They also differ from those stated by IUPAC. Furthermore, it was found that many concepts are dependent on the concept of substance. It is concluded that there must be a greater effort from the community of chemists and the teaching of chemistry in the search for conceptual uniformity to reduce the problems of conceptual understanding. (shrink)