Introduction: Squamous cell carcinoma (SCC) is the most common malignant tumor of oral cavity (O) and esophagus (E). p27 protein has a significant role in biological behavior of the tumors. The purpose of this study was to determine the frequency of p27 expression in OSCC and ESCC.Materials & Methods: Forty paraffin embedded blocks of OSCC & ESCC were collected & clinic pathological data were recorded in this descriptive study. Immunohistochemical staining (IHC) was done for p27 (Kip1) & Labeling Index (percent of positive cells in 10HPF) was calculated and then cases classified in to low (LI£25%) and high (LI>25%) expressions. Statistical analysis was performed by SPSS16 using Fisher's exact and Mann-Whitney tests.Results: Twenty-four cases (60%) were male and 16 cases (40%) were female. The mean age was 65.3±14.3. Twenty five percent of ESCCs and 10% of OSCCs showed high expression of p27. Seventy five percent of ESCC and 90% off OSCC showed low expression and there was no significant difference among OSCCs and ESCCs (P>0.05). There were no significant correlations between age, sex, grade or size of the tumors and p27 expression in OSCCs and ESCCs.Conclusion: Low expression of p27 was found in most of ESCC and OSCC cases.