Gastric cancer is the second most common cause of cancer-related death worldwide and the highest incidence of this cancer has been reported in Asia, especially in China. Identification of early stage lesions is vital in achieving high survival rate. However, due to the lack of reliable biomarkers, the majority of gastric cancer is presented at an advanced stage. Recently, it has been reported that Id-1, a helix-loop-helix protein, may be a valuable diagnostic marker in many types of human cancer. In this study, we evaluated Id-1 protein expression in gastric cancer specimens and compared it with non-malignant tissues. In addition, to investigate whether Id-1 expression levels were associated with the aggressiveness of this disease as implicated in other cancer types, we also assessed Id-1 expression levels in primary tumours and their lymph node metastasized lesions. Our results indicate that up-regulation of Id-1 is a frequent event in gastric cancer but its expression levels are not associated with tumour metastasis. Our evidence provides a possible novel marker for the diagnosis of gastric cancer.