The purpose of this study was to investigate factors affecting the use and non-use of free and low-cost library electronic information resources by information specialists (librarians charged with e-resource responsibilities), academic staff and postgraduate students in scientific, technological and medical (STM) disciplines at universities in Zimbabwe. The research problem was: What are the factors affecting the use and non-use of e-resources by information specialists, academic staff and postgraduate students in scientific, technological and medical (STM) disciplines at universities in Zimbabwe? To address this problem, several sub-questions were set, covering the situation of free and low-cost e-resources available to Zimbabwean universities, factors influencing access to e-resources, the actual use of such resources, and how these problems should be addressed. The study also considered reports from related studies. Using convenience and purposive sampling depending on the participant group, empirical data were collected from information specialists, academic staff and post-graduate students from five universities in Zimbabwe (Africa University, Chinhoyi University of Technology, Midlands State University, National University of Science and Technology and University of Zimbabwe) from May to July 2015. Quantitative and limited qualitative data were collected through questionnaires administered to library directors, information specialists, academic staff and post-graduate students in the STM disciplines. Four library directors or their representatives, 38 information specialists, 80 academic staff, 121 master’s and 14 doctoral students were involved in the study. Descriptive statistical data on all four groups and inferential statistical data on information specialists, academic staff and postgraduate students are provided. Content analysis was applied to qualitative data to reveal views on factors affecting the use of e-resources. The universities provide access to scholarly literature through large collections of e-resources by means of various databases, e-books and electronic theses and dissertations. The availability of journals is no longer a principal problem; the challenge is how to ensure that what is available can be accessed and is used to best effect. Access to computers is also not a problem, especially for information specialists. There are, however, problems with internet infrastructure (i.e. slow and/or unreliable internet, shortage of internet bandwidth), limited user skills and limited user awareness of available library e-resources. Inferential statistical data analysis determined that the position of the information specialist, whether junior or senior, has an important impact on their use of e-resources. Juniors tended to use e-resources more often than seniors. Good technical support when encountering problems with e-resources had the most significant influence on downloading of full-text articles by information specialists. The general linear model test identified lack of skills in using the e-resources as the factor with the highest significance, compared to other variables that had an effect on the use of e-resources by academic staff in STM disciplines. Of the seven significant variables that affected the frequency with which academic staff downloaded full-text articles, the factor of academic staff duties involving research and supervision of students had the highest significance value. On testing factors influencing postgraduate students’ frequency of using e-resources and their frequency of downloading full-text articles, postgraduate students’ training on Google Scholar was established to have the highest significance regarding both. Recommendations include: improved investment in user skills training and information literacy; tools to improve the discoverability of e-resources and content provided by libraries; effective marketing strategies to improve the use and uptake of e-resources by academic staff and students; ensuring that content covered by e-resources is relevant and up to date; providing technical support to e-resource users when they encounter problems; and ensuring adequate IT and internet infrastructure.