Expression profile of 588 known genes relating to tumour biology, was examined between oral squamous cell carcinomas (OSCCs) and matching normal oral mucosal tissues (NOMTs) obtained from Sudanese (n=11) and Norwegian (n=11) patients. cDNA probes were synthesised from total RNA and hybridised with the Atlas human cancer cDNA expression array membranes. RT-PCR and immunohistochemistry were applied to confirm the expression pattern of a subset of the 588 genes. Differences in expression of the genes examined were found between the OSCCs and the NOMTs on the Atlas membranes. Several of these genes were either up- or down-regulated 1.6-fold or higher in the OSCCs compared to the NOMTs in the cases from the two populations. We found that 181 (31%) and 195 (33%) genes were either up-regulated or down-regulated in the OSCCs from the Sudan and Norway, respectively. From the total number of genes (n=376) found expressed in the OSCCs investigated from the two countries, 53 genes (14%) showed common expression profile [35 (66%) were up-regulated and 18 (34%) were down-regulated] and 70 genes (19%) showed opposite regulation status. Results of the RT-PCR and immunohistochemistry confirmed the hybridisation data. These findings may provide an OSCCs-specific gene expression profile in patients from the two countries, suggesting that alterations of 123 genes are common in these OSCCs regardless of ethnic differences or other socio-cultural risk factors between the patients from the two countries. The findings might further suggest that specific genes are frequently involved in these OSCCs, which may provide novel clues as diagnostic, prognostic biomarkers and/or targets for therapy. The Atlas human cancer cDNA expression array technique can be useful to examine and describe the expression profile of known genes frequently involved in OSCCs from different populations.