In the present paper the oxygen balance during a temperature decrease and especially at temperatures close to the liquidus temperature has been studied for lamellar, compacted and nodular cast irons. Extrapolated data from the full scale trial results show that there are significant differences in the level of dissolved oxygen before start of solidification. Earlier research suggest the influence of the dissolved oxygen on the graphite shape, while the present work draws the attention on how the different shaped lamellar-, compacted- and nodular graphite is incorporated in the austenite matrix based on the differences in the dissolved oxygen content. Predicted differences in the dissolved oxygen are also suggested to influence the growth mechanism of the eutectic colonies and the graphite morphologies in the lamellar cast irons.