We hypothesized that the activation of cyclooxygenase (COX)-2, epidermal growth factor receptor (EGFR), and ErbB-2 signaling is required for cervical intraepithelial neoplasia (CIN) lesions to progress to cervical cancer. A retrospective analysis was performed in 179 patients with Stage I squamous cell carcinoma (SCC) and 233 patients with CIN (112 CIN I, 47 CIN II, and 74 CIN III). COX-2, EGFR, and ErbB-2 expression was analyzed by immunohistochemistry using the ACIS III automated imaging system. The mean expression of COX-2, EGFR, and ErbB-2 was compared between the various stages of CIN and SCC. COX-2 mean expression was predominantly cytoplasmic, increasing significantly from CIN I to CIN II, CIN III, and SCC (P<0.001). EGFR mean expression also rose significantly during tumor progression from CIN I to SCC (P=0.001). CIN I samples were negative for ErbB-2 expression. CIN II, CIN III, and SCC were considered positive for ErbB-2 expression in 2.2%, 14%, and 16.2% of cases, respectively. There was also a statistically significant correlation between increase of ErbB-2 positivity from CIN to SCC. We conclude that COX-2, EGFR, and ErbB-2 expression increase significantly during the progression of CIN to cancer.