The present study investigates the vulnerability assessment of the prototype revised Mandatory Rule of Thumb (MRT) buildings initially designed and detailed for three storeys bare frame building;later modified through variable number of storeys (three,four,and five) and different arrangement of infill walls (bare frame,soft-storey,irregular infilled,and fully infilled).The application of infill walls increases the fundamental frequencies,stiffness,and maximum strength capacity,but reduces the deformation capability than the bare frame building.The vulnerability was also reduced through infill walls,where the probability of exceeding partial-collapse and collapse damage reduced by 80％ and 50％,respectively.Furthermore,the increased in storeys (three to five) also increases the failure probability,such that partial-collapse and collapse for fully infilled increases by almost 55％ and 80％,respectively.All obtained results and discussions concluded that the structural sections and details assigned for MRT building is not sufficient if considered as bare frame and soft-storey.And increase in number of storeys causes building highly vulnerable although the infill walls were considered.