Thursday's ruling by an appeals court in Lyon in southeast France was the latest stage in a decade-long legal tussle between Monsanto and farmer Paul Francois, who says he fell ill after inhaling weedkiller Lasso in 2004.
Bayer said in a statement that its options included filing an appeal with France's highest court.
(Reporting by Gus Trompiz; Editing by Sybille de La Hamaide)