A Rifaximin polymorphic mixture of ±/² form in a relative ratio of 85/15 ± 3 and a process for its preparation are herein disclosed. Said polymorphic mixture of Rifaximin is also disclosed for use as a medicament, in particular in the treatment of traveler's diarrhea and hepatic encephalopathy. A pharmaceutical composition comprising said polymorphic mixture of Rifaximin as active ingredient, in particular a solid formulation, more in particular a film coated tablet are disclosed. A polymorphic form of crude wet rifaximin and of purified wet rifaximin and their use as intermediates in a process for the preparation of Rifaximin polymorphic mixture of ±/² form in a relative ratio of 85/15 ± 3 are also disclosed.
