Successful inoculation is not guaranteed and effects may even be deleterious. The main risks are the appearance of types B and D graphite, associated with ferrite and/or carbides due to lack of control of undercooling during eutectic solidification. Alternatively coarse type C graphite in hypo to eutectic grey irons may result from inadequate or excessive inoculation. Sulphur and aluminium content in a molten iron are considered to be the main factors to control the degree of eutectic undercooling, graphite morphology and inoculation efficiency. Thermal conditions, such as superheating, inoculation and pouring temperature play an important role in controlling these effects. Cooling rates due to different mould materials and casting thickness were also considered. In order to resolve individual problems, different inoculant systems have to be considered, such as Sr-FeSi, Ca-FeSi, Ti,Ca-FeSi, Zr,Ca-FeSi, Ba,Ca-FeSi, RE-FeSi (Ca). The present paper made a synthesis of other published papers by the authors, but also added many original un-published results.