Using a computer search, Jon McLoone of Wolfram Research has produced what he believes to be the longest MINIMAL word ladder between two English language words.
Notes: 1) By "minimal", it means that using traditional word ladder rules, there is no chain of words that can connect these two words in FEWER steps. 2) I have not used the definitions from the original source as the dictionary definitions often give away some form of the word. 3) McLoone has noted that his dictionary does not include a number of verb forms (e.g. shorter words with -S, -ED or -ING added), meaning it should be theoretically possible to create a shorter ladder between these words.