The microkinetics of the liquid-phase synthesis of tertiary amyl methyl ether (TAME) from methanol and a mixture of isoamylenes, namely 2-methyl-1-butene and 2-methyl-2-butene, using a macroporous sulphonic acid ion exchange resin as catalyst (Lewatit SPC 118) was determined in a continuous-flow recycle reactor in the temperature range 323-343 K at 1.6 MPa. The reaction proceeds within the gel phase of the microspheres overlapped by a multiple sorption equilibrium between components in the macropore liquid and the gel phase. A kinetic model was developed using the microkinetic data from experiments, where Langmuir sorption isotherms in liquid-phase activities from a modified UNIFAC method were assumed to describe the sorption behaviour of the components. The rate-controlling step, the chemical reaction of sorbed molecules, was formulated according to the homogeneous catalysis as first order in all species. The forward reaction is proportional to the activity ratio of isoamylenes to methanol and the activation energy was determined to be 89.5 kJ/mol.