In thin strip casting of steel surface cracks may occur; it was analysed which influencing parameters are important and how the cracks can be avoided. The studies, mainly with C60-steel, lead to the following results: the cracks are formed during the casting process under high temperatures; on the strip surface hot and colder areas occur, and the cracks have to be studied in both areas separately; mostly transverse cracks are formed; the crack density depends on roll material, - force, - roughness, - surface layers; the cracks are initiated by a temperature break down and by rolling within the pool range.