Sorry, Yes the response content does return the correct data. I did write it to a file and it will uncompress nicely wiht either the UNIX uncompress or gunzip commands. Also, my version of Zlib is 1.11 and the c library for zlib is 1.1.3. Replacing the reference with the content doesn't make any difference. I've also tried the memGunzip function from Compress::Zlib and I get the same error message. Thanks for the checking ideas.