Rheological property (shear stress versus shear rate) of cholesteryl isostearyl carbonate (CISC) is measured as a function of temperature, finding that, like some other cholesteryl derivatives, CISC has blue phases (BPs) between the cholesteric (Ch) and the isotropic (I) phases. In the Ch and the BP phases, measurements of the electrorheological (ER) effect, of the electric field on the rheology, are made; a slight increase of the viscosity is observed in the BPs and no ER effect in the Ch phase, which is contrasted to the distinct ER effect in the nematic (N) and the smectic A (SmA) phases.