I have a 12 mb KML file that I can easily import into QGIS. The trouble is when I save it as a shapefile the data in the description field, which is html, becomes truncated. Is there a way to avoid this?
Shapefiles have a limit of 254 characters and it's possible that you have more characters than what's allowed in your field description. My suggestion would be to check that first and shorten your description. If that's not an option, one way to work around that is to break your descriptions in to multiple fields and then concatenate (please see this thread).
More information about shapefile character limits here
As Jon mentioned above, more information would be best to help find a solution to your question.