In a process for the manufacture of a p-alkylphenol by alkylating phenol with an olefin of 3 to 4 carbon atoms, at an elevated temperature, in the liquid phase, in two reaction zones in series and in the presence of a strongly acidic ion exchange resin as the catalyst, an improvement comprises:(a) passing in a first reaction stage at a temperature of 80.degree.-140.degree. C. over a suspended catalyst, the olefin as a gas at a gas velocity of 30 to 20 cm/second, based on the free cross-section of the empty reactor and on a molar volume of 25 liters per mole of olefin, from below into the reaction mixture; and(b) passing the resulting liquid reaction product, into a second reaction stage, at a temperature of 80.degree.-140.degree. C. over a fixed-bed catalyst;wherein a catalyst having an exchange capacity of 70-120 m. equivalents/100 cm.sup.3 is used in both reaction stages.