New crystal forms of an antibiotic macrolido.

An anhydrous crystalline form or monohydrate of a compound of Formula 1: (See formula) With the proviso that the anhydrous form has a powder X-ray diffraction pattern that has characteristic peaks expressed in 2theta at approximately 6.0, 8, 6, 9.7, 15.4, 15.9, 17.5, 18.2, 18.7 and 21.