Multiple-Access Relay Wiretap Channel In this paper, we investigate the effects of an additional trusted relay node on the secrecy of multiple-access wiretap channel (MAC-WT) by considering the model of multiple-access relay wiretap channel (MARC-WT). More specifically, first, we investigate the discrete memoryless MARC-WT. Three inner bounds [with respect to decode-and-forward (DF), noise-and-forward (NF), and compress-and-forward (CF) strategies] on the secrecy capacity region are provided. Second, we investigate the degraded discrete memoryless MARC-WT, and present an outer bound on the secrecy capacity region of this degraded model. Finally, we investigate the Gaussian MARC-WT, and find that the proposed relay strategies (DF, NF, CF strategies) help to enhance Tekin-Yener’s achievable secrecy rate region of the Gaussian MAC-WT.