In this paper, the unsteady flow of a dusty viscous incom-pressible electrically conducting fluid through a circular pipe is investigated. A constant pressure gradient in the axial direction and a uniform magnetic field directly perpendicular to the flow direction is applied. The effect of dust is described by two parameters f and t, the mass concentration parameter 'f' is a measure of the concentration of dust particles and interaction parameter is a measure of the rate at which the velocity of dust particles adjusts to changes in the fluid velocity and depends upon the size of the individual particles possible limiting cases for t<<1 and t >>1 which corresponds to the case of fine dust and coarse dust respectively. The flow analysis is carried out using differential geometry techniques and analytical solutions of the problem are obtained, with the help of Laplace transform technique. The effect of the magnetic field parameter M, the size of dust particles and the time on velocity, volumetric flow rates and skin friction are determined and discussed with the help of graphs.