Synovial sarcoma have (about in 95% of the cases) the specific and characteristic reciprocal chromosomal translocation t(X; 18) (p11.2; q 11.2). Application of dual-colour fluorescence in situ hybridization (FISH) on interphase nuclei to identify the specific translocation has a diagnostic importance for daily pathological practice. For visualisation of the translocated chromosomal fragments of synovial sarcoma cells on imprint smears, chromosome X painting probes and chromosome 18 centromeric probes were used. Our present study indicates that the precise preoperative diagnosis of synovial sarcoma using dual-colour FISH is possible on smears and this possibility (to identify specific chromosomal translocations in soft tissue tumours) is a landmark in the preoperative diagnosis of soft tissue sarcomas.