Impact tests have been carried out on nodular cast iron in -the cast and forged conditions from -85℃ to 1070℃. The results indicate that nodular cast iron of predominantly ferritic matrix possesses two brittle temperature ranges (below 20℃ and between 550 and 700℃), and one comparatively more ductile range (between 850℃ and 1050℃).The fractures and the bending of the specimens at fracture have also been examined, and these have been correlated to the changes in structure of the matrix in the discussion.Finally, a brief account has been made of the possible applications of the results in the present research in evaluating the applicability of nodular cast iron at various temperatures; and, in particular, in the choice of proper hot working temperatures of this new material. The best hot working temperatures as indicated by the present results have been confirmed by actual forging and upsetting tests under the pneumatic and drop hammers respectively.