Context: Safety-Critical Systems (SCS) are becoming increasingly present in our society. A considerable amount of research effort has been invested into improving the SCS requirements engineering process as it is critical to the successful development of SCS and, in particular, the engineering of safety aspects. Objective: This article aims to investigate which approaches have been proposed to elicit, model, specify and validate safety requirements in the context of SCS, as well as to what extent such approaches have been validated in industrial settings. The paper will also investigate how the usability and usefulness of the reported approaches have been explored, and to what extent they enable requirements communication among the development project/team actors in the development of SCS. Method: We conducted a systematic literature review by selecting 151 papers published between 1983 and 2014. The research methodology to conduct the SLR was based on the guidelines proposed by Kitchenham and Biolchini. Results: The results of this systematic review should encourage further research into the design of studies to improve the requirements engineering for SCS, particularly to enable the communication of the safety requirements among the project team actors, and the adoption of other models for hazard and accident models. The presented results point to the need for more industry-oriented studies, particularly with more participation of practitioners in the validation of new approaches. Conclusion: The most relevant findings from this review and their implications for further research are as follows: integration between requirements engineering and safety engineering areas; dominance of the traditional approaches; early mortality of new approaches; need for industry validation; lack of evidence for the usefulness and usability of most approaches; and the lack of studies that investigate how to improve the communication process throughout the lifecycle. Based on the findings, we suggest a research agenda to the community of researchers and advices to SCS practitioners. (C) 2016 Elsevier B.V. All rights reserved.