Many recent studies from around the world have compared organic and conventional farming systems in terms of soil properties. Microbial biomass and enzyme activity were compared in vineyard soils managed by organic and conventional practices under Mediterranean conditions during the growing. Organic treatments were (i) green manure and farmyard manure at the rate of 30 t ha(-1) (GM1), (ii) green manure and farmyard manure at the rate of 10 t ha(-1), plus E2001 EM Bio-polymer gel solution (GM2), and (iii) green manure plus E2001 EM Bio-polymer gel solution (GM3). Only mineral fertilizers and pesticides were used in the conventional system (CONV). Soil organic C and soil microbial biomass C (SMBC), and protease, urease, alkaline phosphatase, and dehydrogenase activity were significantly higher in the organic system than in the conventional system. The ratio of microbial biomass C to total organic C content (C(mic)/C(org)) was also higher in the organic plots. Total organic C content increased in the organic system by 13%-23% in comparison to the conventional system. Application of GM1 and GM2 resulted in greater microbial biomass and activity as compared to the other management systems. SMBC was significantly correlated with dehydrogenase, protease, urease, and alkaline phosphatase. These results indicate that organic management positively affected biochemical properties, thus improving soil quality and productivity.