The role of microorganisms belonging to the genus Corynebacterium in normalization of vaginal biocenosis by creating acid medium is discussed. A total of 300 samples of lochia and vaginal and cervical secretion were examined, 140 of these taken from women without gynecological diseases and women with a normal course of the postpartum period (controls) and 160 from patients with colpitis of various origins and a complicated course of the puerperium. An appreciable increase of the level of diphtheroids was observed in the lochia of control subjects and in all samples of patients (p < 0.01). Eight species of Corynebacterium were isolated. Urease-negative C. minutissimum, C. equi, C. aquaticum, and C. xerosis predominated in both controls and patients (p < 0.01). Opportunistic C. bovis, C. enzymicum, C. kutshevi, and C. sp. possessing urease activity were seldom isolated. No differences between the 2 groups in the species composition of the isolated bacteria were detected (p > 0.05). Two species of Corynebacterium were sometimes isolated from the same sample, this being more frequently with vaginal and cervical secretion samples than with lochia both in controls and patients (p < 0.01). The most incident association was C. aquaticum and C. equi. 59.6 +/- 2.7 isolated strains proved to be sensitive to antibiotics manufactured in this country.