<p>Provided is a novel polymorphic form I of rifaximin and a process for preparation thereof. The novel polymorphic form I is characterized by powder x-ray diffraction pattern at 2T 5.2, 7.2, 8.4 and 8.7 degrees±0.2 and water content within the range of 2.0 to 4.5%. A process for preparation of novel polymorphic form I by treating rifaximin with a mixture of ethyl alcohol and water is also provided.</p>
