Allelic deletions on the short arm of chromosome 8 (8p) are frequent events in many different types of malignant tumors, including head and neck tumors and oropharyngeal cancers. These regions are thought to harbor tumor suppressor genes. However, there has been no detailed analysis of loss of heterozygosity (LOH) on the chromosome arm 8p in oral squamous cell carcinoma (SCC). In order to estimate details of 8p loci involved in oral SCC, 32 patients with oral SCCs were examined for the LOH state 8p by PCR-LOH assay using 14 microsatellite markers. Based on our results a detailed deletion map of 8p showed LOH in at least one of the loci tested in 62.5% (20 of 32) of patients; and microsatellite instability (MI) was observed in 50% (16 of 32). The frequent LOH on this chromosome arm was identified at D8S87 and D8S258, mapped on 8p12 and 8p22, respectively. Fisher's exact test revealed no significant statistical correlation between the incidence of LOH or MI and clinicopathological features. Our observations indicate that the short arm of chromosome 8 may play a role in the pathogenesis of oral SCC; and that the two loci identified in this study may be tumor suppressor gene loci on 8p.