Method of treating bacterial vaginosis in a subject in need thereof involving administering to the subject a therapeutically effective amount of secnidazole in a microgranule formulation, wherein the microgranule formulation comprises a plurality of microgranules having a volume-weighted particle size distribution within a microgranule population, wherein the volume-weighted particle size distribution as measured from a representative sample of the microgranule population comprises (a) 10% of the microgranule population having a volume-weighted particle size about no less than 470 micrometers; (b) 50% of the microgranule population having a volume-weighted particle size between about no less than 640 micrometers and about no more than 810 micrometers; (c) 90% of the microgranule population having a volume-weighted particle size about no more than 1170 micrometers; or (d) a combination thereof, which can include some or all of (a) through (c) above.