Select MAX phase-based ceramics were screened with respect to their potential susceptibility to environmentally-assisted degradation in an oxygen-poor liquid lead-bismuth eutectic (LBE) environment, both under static and fast-flowing exposure conditions. The majority of the MAX phases exposed to oxygen-poor ( 2.210-10 mass%) static liquid LBE for at least 1000 h at 500°C showed exceptional chemical compatibility with the heavy liquid metal, i.e., no evidence of LBE dissolution attack was observed, despite the absence of a continuous oxide scale on the surface of the exposed MAX phase ceramics. The local LBE interaction observed only with the Zr-rich MAX phases consisted in the partial substitution of Al by Pb/Bi in the MAX phase crystal structure and the in-situ formation of Pb/Bi-containing solid solutions. Moreover, the interaction of Zr-based MAX phases with static liquid LBE was accompanied by the dissolution of parasitic intermetallic phases, which facilitated the further LBE ingress into the ceramic bulk. The erosion resistance of select MAX phase ceramics was also assessed in oxygen-poor ( 510-9 mass%) fast-flowing (v ≈ 8 m/s) liquid LBE for 1000 h at 500°C. Despite the moderate LBE oxygen concentration, oxidation was the predominant corrosion mechanism, while no erosion damages were observed in the exposed MAX phase ceramics. The resistance of the MAX phase ceramics to both dissolution corrosion and erosion in contact with oxygen-poor Highlights  Exposing 11 MAX phases to oxygen-poor, static LBE showed little or no interaction.  The LBE/Zr2AlC interaction formed a new Zr2(Al,Pb,Bi)C MAX phase solid solution.  The LBE/(Zr,Ti)n+1AlCn interaction formed (Zr,Ti)n+1(Al,Pb,Bi)Cn solid solutions.  (Nb,Zr)4AlC3 showed the best erosion resistance in oxygen-poor, fast-flowing LBE.  MAX phases outperformed 316L stainless steels exposed to similar LBE conditions. Recently, Bentzel et al. studied the behaviour of several MAX phases in static liquid sodium, another Gen-IV coolant, up to 750°C for 168 h [21]. They reported that Ti3SiC2, Ti2AlC and Cr2AlC were stable, as well as their grain boundary phases. Ti3AlC2, however, showed signs of degradation along the grain boundaries and Al-depletion in the MAX phase grains [21].