Monty Python and the Holy Grail producer Mark Forstater claims that he has not received his due share of proceeds from the hit musical, which is described on its posters as being "lovingly ripped off from" the Holy Grail film.
Eric Idle, Michael Palin and Terry Jones will all give evidence at London's High Court next week,
BBC News reports.
Terry Gilliam and John Cleese are both currently out of the country, and are not expected to be present. Sixth Python Graham Chapman died in 1989.
Forstater and his company Mark Forstater Productions Ltd have brought the claim against Python (Monty) Pictures Ltd, which represents the film interests of the Python team, and Freeway Cam (UK) Ltd.
The claimant's lawyer Tom Weisselberg asserted in court today that "for financial purposes" his client should be regarded as "the seventh Python".
Under the terms of a 1974 agreement, investors like Forstater became entitled to a share in 50% of all merchandise and spinoff revenues relating to the movie.
Forstater asserts that his share is one-seventh of that 50% figure - the same share enjoyed by the surviving Pythons - under the contract. Since 2005, he has been paid as if he is entitled to a one-fourteenth share.
The five-day hearing continues next week.