The download below includes the original install disks for MASM 6.11, along with patches to upgrade to 6.11d (last version that runs on DOS/Win16) and 6.14 (includes support for the Intel Pentium Pro processor, the Intel MMX architecture, AMD 3D Technology, and Intel Internet Streaming SIMD Extensions).
Also included are the user's manuals in both Word and PDF format.
Note: MASM is no longer sold by Microsoft, and the MASM executable and linker can be found in other tools available for free directly from Microsoft. Therefore, I am making it available for download here. If you represent Microsoft and want this download removed, please contact me.