This study was performed to determine whether there is a linear correlation between serum squamous cell carcinoma (SCC) antigen levels and tumor volumes in patients with cervical carcinoma. Sera from 43 patients with stage IIb bulky (>4 cm) cervical carcinoma were collected prospectively and assayed for SCC antigen levels before, and 2 weeks after, three courses of neoadjuvant chemotherapy. At the same time, tumor volume was measured by pelvic magnetic resonance imaging (MRI). Mean serum SCC antigen level declined significantly after neoadjuvant chemotherapy, from 16.8 ng/ml (range 0.4-80.2 ng/ml) to 3.1 ng/ml (range 0.1-13.0 ng/ml) (P = 0.0001). Also, the percentage of patients with elevated serum SCC antigen level decreased significantly from 79.1 to 25.6% (P < 0.001). Furthermore, mean tumor volume also declined significantly after neoadjuvant chemotherapy, from 54.1 cm3 (range 8.4-133.9 cm3) to 5.3 cm3 (range 0-77.8 cm3) (P = 0.0001). However, serum SCC antigen levels did not show a linear correlation with tumor volumes before and after neoadjuvant chemotherapy (r = 0.0776, P = 0.6208; r = 0.1887, P = 0.2256, respectively). Interestingly, the percentage reduction in serum SCC antigen levels showed a linear correlation with that of tumor volume after neoadjuvant chemotherapy in 34 patients who had elevated prechemotherapy serum SCC antigen levels (r = 0.5094, P = 0.0021). These results suggest that although serum SCC antigen level does not have a direct linear relationship to tumor volume, reduction in serum SCC antigen level has a linear correlation with that of tumor volume after neoadjuvant chemotherapy in patients with cervical carcinoma and elevated prechemotherapy SCC antigen levels.