Process for the manufacture of a disazo dyestuff of the formula ##STR1## in which R.sub.1 and R.sub.2 each stand for hydrogen, chlorine, bromine, alkyl of 1 to 4 carbon atoms or alkoxy of 1 to 4 carbon atoms, R.sub.3 and R.sub.4 each stand for hydrogen, chlorine, bromine, nitro, trifluoromethyl, alkyl of 1 to 4 carbon atoms or alkoxy of 1 to 4 carbon atoms; and the hydroxyl groups each stand in 2- or 4-position to the azo groups which comprises diazotizing a 2- or 4-hydroxy-4'-aminoazobenzene of the formula ##STR2## in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are defined as above, with an alkali metal nitrite in an aqueous mineral acid, the normality of which being about 10.sup.-2 to 5, in the presence of a phenol capable of being coupled of the formula ##STR3## in which R.sub.1 and R.sub.2 are defined as above and subsequently reacting the diazonium salt obtained with the phenol by raising the pH to a value between about 3 and 11, the surprising feature of this process (diazotization in the presence of the phenol) being that practically no nitrozation or a nitration of the phenol occurs.