New crystalline form.

crystalline azithromycin sesquihydrate, characterized as having a 13C NMR spectrum in solid state having a plurality of peaks with chemical shifts of about 179, 5ppm, having a single peak separation between 0 ppm and 0, 3 ppm; 10, 4 ppm; 9, 9 ppm; 9, 3 ppm; 7, 6 ppm; 6, 5 ppm; wherein said peaks may show variation in chemical shift of n0, 2 ppm.