Maybe that's something the ZipOutputStream does. IAC, as mentioned earlier I don't think it will achieve what you want. Look under "Creating and Modifying Zip Files" in http://msdn.microsoft.com/msdnmag/issues/03/06/ZipCompression/default.aspx

To add to an existing ZIP you will need to copy it into a new one and use that for the additions....

>I tried this already:
>

FileOutputStream filOpStrm = new FileOutputStream(zipFileName,true)

>
>The file is overwritten anyhow.
>
>
>
>>>I'm modifying the code in the Zip method here http://www.codeproject.com/KB/cs/unzipC_usingJ_.aspx
>>>
>>>This code creates the ZIP file:
>>>

FileOutputStream filOpStrm = new FileOutputStream(zipFileName);

>>>
>>>If the file already exists, I want to add to it. How do I get a reference to the
>>>file without recreating it?
>>

FileOutputStream filOpStrm = new FileOutputStream(zipFileName,true)

>>But that looks like you'd be concatenating ZIP files and I don't think it will work.
>>
>>HTH,Viv