RESUMEN Introduccion: Lippia alba (Mill) N.E. Brown es una planta aromatica perteneciente a la familia Verbenaceae, ampliamente usada en Suramerica y Norteamerica como infusion contra la hipertension, problemas digestivos, nauseas y resfriados. Objetivo: En el presente estudio, se evaluo la actividad antiviral in vitro frente al Herpesvirus Humano Tipo 1 (HSV-1), de veinte aceites esenciales de L. alba y, diez de sus componentes mayoritarios. Metodologia: La actividad antiviral in vitro fue evaluada empleando la tecnica modificada, de titulacion del punto final (EPTT). Los aceites esenciales, de plantas de L. alba recolectadas de diferentes regiones del pais, fueron obtenidos por hidrodestilacion asistida con radiacion de microondas (MWHD). Se determino por cromatografia de gases–espectrometria de masas (GC-MS), la composicion quimica, de los veinte aceites esenciales de L. alba, identificandose dos quimiotipos: citral y carvona. Resultados y conclusiones: Los aceites quimiotipo carvona, BC 1 y CA 2 , mostraron actividad antiherpetica in vitro, moderada sobre monocapa de celulas HeLa infectadas, con valores de R f de 1x10 1,5 , en concentraciones, de 250μg/mL y 125μg/mL, respectivamente. Los controles positivos, sulfato de heparina y aciclovir, redujeron el titulo viral con valores de R f , en orden, de 1x10 2 y 1x10 4 . Ninguno de los monoterpenos evaluados mostro actividad contra el HSV-1. Salud UIS 2010; 42: Palabras clave: Lippia alba (Mill) N.E. Brown, herpesvirus humano 1, agentes antivirales , aceite esencial, verbenaceae ABSTRACT Introduction: Lippia alba (Mill.) N.E. Brown is an aromatic shrub belonging to the Verbenaceae family, which is widely used all over South and Central America as an infusion against, hypertension, digestive troubles, nausea and cold. Objective: The antiviral activity in vitro against Herpesvirus 1, Human (HSV-1) of twenty essential oils of L. alba and ten of its components were evaluated. Methodology: The antiviral activity was determined using a modified end-point titration technique (EPPT). The essential oils from L. alba collected in different regions of Colombia were obtained by microwave-assisted hydrodistillation (MWHD). Their chemical compositions were determined by GC and GC/MS. Two chemotypes were distinguished, characterized by carvone and citral as main constituents. Results and conclusions: Carvone chemotype oils BC 1 and CA 2 were found to be moderate antiviral activity over infected confluent monolayers of HeLa cells with R f value of 1x10 1,5 at a concentration of 250μg/mL and 125μg/mL, respectively. Heparin sodium salt and acyclovir were used as positive controls and showed R f values of 1x10 2 and 1x10 4 , respectively. None of monoterpenes tested showed antiviral activity against HSV-1. Salud UIS 2010 ; 42: Keywords: Lippia alba (Mill) N.E. Brown, herpesvirus 1, human, essential oil, antiviral agents, verbenaceae