I guess this is a boost/bjam bug... What I did was: 1. download and uncompress boost-1.33.1, build bjam.exe 2. download official zlib package and unpack to c:\zlib 3. run $ bjam -sTOOLS=mingw -sNO_COMPRESSION=0 -sNO_BZIP2=1 -sNO_ZLIB=0 -sZLIB_INCLUDE=c:/zlib/include -sZLIB_LIBPATH=cL/zlib/lib -sZLIB_BINARY=zdll --prefix=c:/boost --with-iostreams install bjam says something like bzip2 support is disabled, which I interpret as zlib is supported, and produces .lib, .dll without problem. 4. After numerous failed links, I had a look at boost_1_33_1\bin\boost\libs\iostreams\build\libboost_iostreams.lib\mingw\debug and found only two object files, no zlib.obj! 5. I read the manual again and see ZLIB_SOURCE needs to be specified, I download zlib source, and add option -sZLIB_SOURCE=c:\zlib\src. This time, I get error message: unknown dependent target <@boost!libs!build>libboost_zlib.lib. 6. If I copy the iostream source files (except for bzip2.cpp) to my project and compile, everything is OK and no zlib source is ever needed. Conclusions: 1. bjam should report error if NO_COMPRESSION=0 and NO_ZLIB=0, but zlib.cpp can not be compiled for any reason. 2. Why zlib source is needed? 3. How can I build iostreams with zlib under windows/mingw? Many thanks in advance. Bo