The effect of heat treatment (70, 80 and 95°C, for 1, 3 and 10 min) on the rennet clotting time (RCT) has been evaluated in cow milk (Bruna Italiana) and in the milks of five goat breeds (Saanen, Camosciata, Ionica, Garganica and Maltese). The RCT of raw cow milk ranked at an intermediate level compared to that of raw milk of goat breeds examined. With respect to the raw milks, the RCTs of cow milk became progressively longer as a function of both heating temperature and time, while all the goat milks' RCTs decreased. Significant (P<0.05 or <0.001) decreases have been registered in the RCTs of the Camosciata, Ionica, Garganica and Maltese goat milks even after mild heating (to 70°C for 1 min), while significant (P<0.05) variations have been observed in the Saanen goat milk only with intense heating (95°C for 1, 3 and 10 min).