The most common type of gallbladder cancer is adenocarcinoma. Primary squamous cell carcinoma of the gallbladder is a rare and aggressive disease. It is responsible for up to 1.7% of the malignant neoplasms of the gallbladder. It characteristically presents with invasive growth, a low tendency towards lymph node metastasis and a high incidence of local infiltration and hepatic metastasis, presenting a worse prognosis than adenocarcinoma of the gallbladder. Cases of gallbladder cancer forming a fistula to the stomach are also rare. We experienced a case of primary squamous cell carcinoma of the gallbladder which formed a fistula to the stomach. (Korean J Gastrointest Endosc 2010;40:285-289)