Bacterial vaginosis (VB) is a syndrome characterized by overgrowth of endogenous Gram negative bacterial flora and the lack of the normal flora. Within bacterial enzymes, sialidases have been considered a virulence factor of many pathogenic microorganisms colonizing the different mucous membranes. Their presence in vaginal discharges can be correlated with VB. The aim of this study was to detect the activity of this enzyme in women with this syndrome and without clinical evidence of genital infection. Out of a total 112 women studied, 51 were patients with VB and the other 61 women presented normal vaginal flora. For the quantification of enzyme activity, the technique based on the enzymatic hydrolysis of a derivative acid of the acetyl metoxifenil muramic acid was used. In the studied population both groups shared values from 0.5 to 5.1 nmoles of metoxifenol, whereas only 11 out of 52 patients with VB (21.17%), registered more than 5.1 nmoles. The presence of sialidase activity is not enough to confirm VB, except for values greater than 5.5 nmoles of the metoxifenol produced in the enzymatic reaction.