The fungi growth on Spanish ham surfaces appears to be involved in theflavor development of this product. However, there is a lack of information about the metabolic activity of these molds. Five mold strains belonging to the Penicillium genera, isolatedfiom Spanish ham su$aces were used to evaluate their proteolytic activity in a meat substratum having a similar composition to that existing on the Spanish ham suvace. All samples were held at different temperatures (3, 8 and 12C) and relative humidities (75%, 85% and 95%) during 30 days. All of the molds reflected a proteolytic activity which was principally affected by temperature, and the samples inoculated with P. chrysogenum strains proved to achieve the highest proteolytic activity.