In order to optimize the process of cheesemaking of Serra cheese, the most famous traditional portuguese cheese manufactured with raw ewes＇ milk at farm level, several cheeses were produced according to a second-order composite factorial design using temperature of coagulation, amount of plant rennet added and amount of salt added to fresh cheese as the manipulated technological variables. Sensory, microbiological, physicochemical and biochemical analyses were carried our for all experimental cheeses and for two cheeses manufactured by traditional practices. The amount of salt added to fresh cheese affected significantly the sensory, microbiological and biochemical characteristics of 60 day-old Serra cheese, whereas the amount of plant rennet added and the coagulation temperature affected significantly only the sensory and microbiological attributes. None of the three technological parameters at the levels tested played a statistical role at the 5% significance level in the chemical composition of the cheese. It was found that 0.3 g of plant rennet added per litre of milk, a coagulation temperature of 28 degrees C, and 0.05 g of salt added per cm(2) of fresh cheese surface provide the best quality of cheese in terms of highest sensory scores and lowest numbers of viable enterococci and coliforms.