The type , morphology and sources of inclusionin steels ,includingindigenous and exogenous inclusions ,were discussed and reviewed .Indigenous inclusions are deoxidation products or inclusions precipitated during cool-ing and solidification of steel . Exogenous inclusions arise pri marily fromthe incidental chemical (reoxidation) andmechanical interaction of liquid steel with its surroundings (slag entrainment and erosion of lining refractory) .Types and causes for the nozzle clogging were also summarized . Reasons for bubble formation and bubble size dis-tribution in steels were discussed thereafter .Finally , morphology and causes of inclusion-related defects in contin-uously cast steel products were reviewed ,such as flange cracking in cans ,slag spots and line defects on strips . The type, morphology and sources of inclusionin steels, including indigenous and exogenous inclusions, were discussed and reviewed. Indigenous inclusions are deoxidation products or inclusions precipitated during cool-ing and solidification of steel. Exogenous inclusions arise pri marily from the incidental chemical (reoxidation) and mechanism interaction of liquid steel with its surroundings (slag entrainment and erosion of lining refractory) .Types and causes for the nozzle clogging were also summarized. Reasons for bubble formation and bubble size dis-tribution in steels were discussed subsequently. Finally, morphology and causes of inclusion -related defects in contin-uously cast steel products were reviewed, such as flange cracking in cans, slag spots and line defects on strips.