This paper investigates the potential of clove (Eugenia caryophyllata) essential oil (C-EO) as a wood protection system for use in cultural heritage conservation. The preventive and curative antifungal efficacy of C-EO was compared to a boron containing wood preservative (Diffusit S) in two laboratory tests on European beech (Fagus sylvatica) and Scots pine sapwood (Pinus sylvestris) mini-blocks. Non-sterile, air-infected wood samples were employed in the first test, while wood samples with active attack, as result of inoculation with three fungal strains isolated from cultural heritage sites, in the second test. Untreated controls and C-EO-treated wood blocks were incubated up to 150 days to monitor and quantify fungal growth. The experimental results showed antifungal efficacy of C-EO to be higher than that of the boron wood preservative at the concentrations used. Concentrations of C-EO 5 % - 10 % in ethyl alcohol prevented mould growth for at least 150 days, while a concentration of 10 % delayed or suppressed active attack by decay fungi. This effect, determined up to 90 days of incubation, was dependant on the type of fungus.