Overexpression of cellular inhibitor of apoptosis protein 1 (cIAP-1) has been demonstrated in a variety of human cancers and found to be associated with lymph node metastasis, clinical stage, recurrence, and prognosis of these cancers. In this study, we examined the expression of cIAP-1 protein in 73 specimens of oral squamous cell carcinoma (OSCC), 76 specimens of oral epithelial dysplasia (OED), and 31 specimens of normal oral mucosa (NOM) by immunohistochemistry (IHC). The cytoplasmic cIAP-1 labeling indices (LIs) in OSCC, OED, and NOM samples were calculated and compared among the groups. Correlations between the cytoplasmic cIAP-1 LIs in OSCCs and clinicopathological parameters and survival of OSCC patients were analyzed statistically. We found that the mean cytoplasmic cIAP-1 LIs significantly increased from NOM (23%±22%) through OED (50%±25%) to OSCC samples (73%±17%) (p=0.000). A significant correlation was found between the higher mean cytoplasmic cIAP-1 LIs and OSCCs with positive lymph node metastasis (p=0.000) and more-advanced clinical stages (p=0.045). However, the expression of cIAP-1 protein was not associated with OSCC patient survival. Our results suggest that the increased expression of cIAP-1 is an early event in oral carcinogenesis, and clAP-1 may be a biomarker for OSCCs. Measuring the amount of cytoplasmic cIAP-1 expression in OSCC samples may predict the oral cancer progression in Taiwanese patients.