This page describes how to obtain a Tcl/Tk source release. See Binary distributions for obtaining pre-built binaries.
The main site for Tcl/Tk source distributions is SourceForge.
The latest downloads for the Tcl 8.6 and 8.7 release sequences are shown in the table below. Older releases are also available from the above sites.
The source releases include make files for Windows, Unix and Xcode project files for Mac OS X.
Once you've retrieved the sources, see How to Compile Tcl Source Releases.
Unix (including Mac OS X)
You'll want both Tcl and Tk sources; choose the gzipped tar format. The files listed under the Windows sources contain the same information but are in ZIP format.
Gzip'ed Tar Files
Extract gzip'ed archives with this UNIX command line:
gunzip < file.tar.gz | tar xvf -
If you have downloaded the Unix version of these files, there is
no need to also download these versions since these files are
identical but in ZIP format instead of compressed tar.