The aim of the study was to determine whether or not the tyrosine kinase receptor ERBB2 is overexpressed in synovial sarcomas (SSs). We also focused on the cell cycle-related nuclear protein-Ki-67. Thirty-two samples were available for immunohistochemistry and only 1 case revealed a weak diffuse membrane ERBB-2 staining. The remaining cases showed either no staining (20 cases) or weak focal membrane staining (9 cases). In our 3 highly overexpressed ERBB2 mRNA samples, fluorescence in situ hybridization showed no amplification of the ERBB2 gene. ERBB2 mRNA expression was present in all samples of SSs at a comparable level to that in breast carcinoma control group, with a 2+ or 3+ immunopositivity. The high level of ERBB2 mRNA expression correlated with a high level of Ki-67 mRNA. The level of Ki-67 mRNA correlated with Ki-67 protein expression. The study shows that ERBB2 mRNA expression is very strong in SSs, but the membrane ERBB-2 protein expression is practically absent.