The lipid monocaprin (1-monoglyceride of capric acid) has been shown to be effective against enveloped viruses such as herpes simplex virus HSV in vitro. As it is known that HSV can develop resistance to acyclovir which is the most common treatment used, it was considered to be of interest to formulate a cream containing the lipid monocaprin as the active substance against HSV. The aim of this study was to develop an o/w-emulsion (cream) containing monocaprin and to evaluate the effects of formulation variables on the virucidal activity of monocaprin as well as the in vitro release rate of the monoglyceride from the formulations. The results show that release rate and extent of monocaprin release as well as the microbicidal properties of the the o/w-emulsion formulations are affected by the proportion of the oil phase and the amount of carbomer in the aqueous phase. Reducing the oil volume fraction increased antiviral effect and release of monocaprin from the formulation.