Five cases of clonal karyotype evolutions in solid tumours in children are presented. In four cases, an evolutionary pattern far more complex than usually seen in human leukemias was observed. Besides the loss and acquisition of chromosomes and polyploidization, these tumours were mainly characterized by the occurrence of multiple more or less complex translocations. These translocations were either balanced or unbalanced. In only one case were no structural aberrant chromosomes seen. In that tumour, the evolutionary mechanisms were merely the loss or gain of chromosomes and polyploidization. Its evolutionary pattern was of the type most frequently seen in leukemias.