Method for revamping a multi-bed ammonia converter, wherein said converter comprises a plurality of adiabatic catalytic beds including a first catalytic bed and one or more further catalytic bed(s), said catalytic beds being arranged in series so that the effluent of a bed is further reacted in the subsequent bed; at least a first inter-bed heat exchanger arranged between said first catalytic bed and a second catalytic bed to cool the effluent of said first bed before admission into said second bed, and optionally further inter-bed heat exchanger(s) arranged between consecutive beds; said method involves the conversion of said first catalytic bed into an isothermal catalytic bed.