(57) An asphalt is modified by mild oxidation, with for example, air, oxygen or hydrogen peroxide, at a tempe- ratur of 140°C to 170°C for up to one hour such that the softening point of the asphalt is not materially altered. Substantially reduced reactivity toward sulfur is imparted. Such a mildly oxidised asphalt can be treated immediately with sulfur at a temperature of 120°C to 170°C form a sulfur modifier product. Alternatively, the mildly oxidised product can be stored hot and subsequently treated with sulfur, for example, at a road-making site, without the high hydrogen sulfide evolution often encountered with known products.