Genetic alteration of p53 is a significant determining factor in the carcinogenesis. The loss of function, mutant p53 can possess a dominant negative effect on wild-type p53 and may also exert gain-of-function activity. It is, however, not clear how p53 functional status due to various types of mutation results in outcome of patients with oral cancer. A total of 60 oral SCC samples were subjected to yeast functional assay that screens human p53 function in yeast, and sequencing for determination of p53 mutations. The detected mutants were further investigated for their dominant negative activity using a yeast-based transdominance assay that tests dominant negative activity of a mutant p53 over wild-type p53 by coexpressing the mutant and wild-type p53 in a yeast transcriptional reporter system. p53 mutation was found in 42 out of 60 of which 10 (24%) exhibited dominant negative activity and 32 (76%) without dominant activity (recessive mutation). The remaining 18 (30%) were considered to have wild-type p53. The patients with dominant negative mutation had significantly shorter disease-free survival than patients with no mutation (log-rank test, p<0.001) and those with a recessive mutation (p<0.016). There were slight significant differences in disease-free survival were found between the patients with tumours harbouring a recessive p53 mutation and those with tumours harbouring a wild-type p53 (p<0.038). The presence and absence of a dominant negative p53 mutation may thus provide a predictor of early recurrence in oral SCC patients.