The interactions of the Pt/Ni/Cu and Au/Ni/Cu structures and their ambient dependence are studied. Comparison of the Pt~~Cu interdiffusion with that of Au-Cu across the Ni layer shows an interesting relation between the interactions and their ambient dependence. According to the surface potential model, which has been shown to correlate the ambient effects for many systems, diffusion of both Pt and Au into the Cu layer via the Ni layer should be enhanced by oxygen. This is observed for Au but not for Pt. On the other hand, the anticipated oxygen-enhanced diffusion of Cu into Pt and Au layers via the Ni layer is observed in both structures. The difference between the Pt and Au diffusion via Ni is attributed to the presence of competing interdiffusion between Pt and Ni in the Pt/Ni/Cu structure, which is reduced by oxygen, whereas little diffusion of Ni into the Au layer is observed for the Au/Ni/Cu structure. The ambient effects on the trilayer structures are compared with those on the binary Au/Ni, Au/Cu, Ni/Cu, Pt/Ni, and Pt/Cu structures. The diffusion mechanisms are discussed, and relations among various systems are suggested. © 1987, Materials Research Society. All rights reserved.