The present report describes the case of a 21-mo-old boy with a fetal rhabdomyomatous nephroblastoma (FRN) diagnosed by fine-needle aspiration cytology (FNAC). The smears contained numerous isolated or clustered, deeply eosinophilic, thin, elongated rhabdomyoblasts with oval nuclei. Some of these cells presented cross-striations. Peculiar clusters of small, deeply eosinophilic, round cells with and without rounded nuclei in a mosaic pattern were interpreted as representing transversally oriented rhabdomyoblasts. Fetal rhabdomyoblasts were by far the predominant type of cell. Histology of the surgical specimen proved 90% of the mass to be constituted of fetal rhadomyomatous tissue. Adequate recognition of FRN is useful for the planning of treatment.