Abstract: A distributed optimal control problem for a system described by a bio-heat equation for a homogeneous plane slab of tissue is analytically investigated. The required tissue temperature at a particular location of the tumour in hyperthermia can be attained within the total operation time of the process due to induced microwave radiation which is taken as control. The tissue temperature against the tissue length at different operation time of the process is considered to attain the desired temperature of the tumor.