In this study, two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF-MS) technology was used to examine differentially expressed proteins in oral squamous cell carcinoma (OSCC) tissues from Norway (n=15) and the UK (n=45). Twenty-nine proteins were found to be significantly overexpressed in the OSCCs examined compared to the normal controls. Identified proteins included, family of annexin proteins that play important roles in signal transduction pathways and regulation of cellular growth, keratin-1, heat-shock proteins (HSP), squamous cell carcinoma antigen (SCC-Ag), cytoskeleton proteins, and proteins involved in mitochondrial and intracellular signalling pathways. The expression of four selected proteins (annexin II and V, HSP-27, and SCC-Ag) was verified using western blot analysis of 76 fresh tissue biopsy specimens in total, from Norway (n=53) and the UK (n=23). Proteomic analysis of OSCCs examined here demonstrated involvement of several proteins that might function as potential biomarkers and molecular targets for early cancer diagnostics, and may contribute to a novel approach to therapeutics and for predicting prognosis of OSCC.