The flow of blood in human circulatory system can be controlled by applying appropriate magnetic field. We have applied magnetic field in some problems of blood flow. It is observed that the fluid velocity, the wall shear stress and the pressure drop decreases as the magnetic parameter increases. It may help the medical practitioners to control the blood flow of a patient of high blood pressure, hypertension, haemorrages. Also observed that the wall shear stress and damages to the wall can be reduced by applying magnetic field. The purpose of this work is to draw the attention of the learned men of medical profession, research scholars and various investigators and to inform them about the existence of a large scope for further research and exploration in this field of medical science.