Retinoblastoma is a malignant tumourous disease which occurs in childhood. The most important factors which influence possible cure of patients with a retinob- lastoma are early detection of the disease, correct diagnosis and adequate therapy. In the submitted case-record the authors provide evidence of the importance of cytological examination of cerebrospinal fluid which is important in retinoblas- toma in particular for the follow-up of treatment. Cytological examination of cerebrospinal fluid in this type of tumour is very reliable and can reveal infiltra- tion of tumour cells into the CNS much sooner than imaging methods.

        Key words: retinoblastoma, cytology of cerebrospinal fluid, infiltration of the