When telomeres are shortened to a critical length, they will initiate chromosomal instability (CIN) and may finally cause tumorigenesis. The purpose of the present study was to evaluate the shortened telomere as a potential biomarker for tumorigenesis in gastric carcinoma. The telomeres in matched cancer and adjacent noncancer mucosa samples from 86 gastric carcinoma patients were measured by real-time polymerase chain reaction (PCR). According to the International Union Against Cancer (UICC), tumor stages were classified into four groups: stage I (n = 23), stage II (n = 20), stage III (n = 23), and stage IV (n = 20). Telomere length decreased with aging in both adjacent noncancer mucosa and cancer tissue (r = -0.261 (P = 0.008) and r = -0.27 (P = 0.012), respectively). The telomere length of UICC stage I tumors was significantly shorter than the average telomere length in adjacent noncancer mucosa (P = 0.023). Telomere length increased gradually with increasing UICC stage (P = 0.032). The telomere length of UICC stage IV tumors was significantly longer, when compared to that in noncancer mucosa (P = 0.019) and stage I tumors (P = 0.002). In summary, telomere length undergoes shortening in early stage gastric carcinoma and lengthening in advanced gastric carcinoma. Additionally, telomere shortening may initiate the tumorigenesis of gastric carcinoma.