The in vitro antiviral activity of the essential oil from Minthostachys verticillata was investigated against herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PrV). The viral inhibition was assayed employing viral plaque reduction assay. The antiviral activity of the essential oil specifically affects PrV and HSV-1 multiplication, since it was found that non toxic effects on cells were observed at the concentrations assayed. The therapeutic index values were 10.0 and 9.5 for HSV-1 and PrV, respectively. The antibacterial activity was studied using a diffusion assay and the broth tube dilution method. Gram-positive bacteria were more sensitive to inhibition by plant essential oil than the gram-negative bacteria. The essential oil of M. verticillata was analyzed by gas chromatography (GC) technique. Of the six components identified in the volatile oil, pulegone (44.56%) and menthone (39.51%) were the major constituents. The antimicrobial activity can be explained to some extent by the presence of pulegone. Results suggest that further investigations concerning the isolation of the substance responsible for the antimicrobial activity and an effort to define the mechanisms of action are warranted.