In attempts to characterize Portuguese whey cheese (Requeijao) and optimize the manufacture thereof, 17 whey cheeses were produced according to a factorial design using heating time, heating temperature and fractional addition of ovine/caprine milk as manipulated technological variables. Chemical analyses were carried out for the 17 cheeses, whereas sensorial and rheological analyses were carried out for eight selected whey cheeses and a reference (i.e. a whey cheese produced locally according to traditional procedures). A true local maximum exists for moisture content (at a temperature of about 93 degrees C, heating time of about 30 min and addition of about 17% ovine milk) which lies well within the range chosen for experimentation. Fat content of Requeijao was positively affected by heating temperature (especially via its quadratic effect) and, to a lesser extent, by heating time (especially via its linear effect); nitrogen content was especially affected by heating temperature (via its quadratic effect); and moisture content was affected especially by heating temperature (via its quadratic effect). The sensorial analyses showed that the eight whey cheeses produced were preferred with respect to the reference whey cheese. Far rheological analyses the most significant observations pertain to the high strain dependence of the dynamic moduli, absence of a true equilibrium storage modulus, and relatively low difference between the loss and the storage modulus.