Choriocarcinoma is a rapidly invasive, widely metastatic human chorionic gonadotropin (HCG)-producing neoplasm, usually intrauterine and gestational. Primary gastric choriocarcinoma is very rare, and its pathogenesis is still uncertain. We report a case of primary gastric choriocarcinoma associated with adenocarcinoma in a 36-year-old woman. The patient presented with gastrointestinal bleeding and a gastric mass clinically suspicious of gastric adenocarcinoma. Histopathologic evaluation proved the tumor to be a choriocarcinoma, with a minor component of a poorly differentiated adenocarcinoma. The patient was treated with a standard nongestational choriocarcinoma chemotherapy regimen. An impressive initial response was evidenced by clinical reduction of the tumor volume and drop of the serum beta-HCG levels after the first cycle. However, the tumor rapidly recurred in the abdomen and disseminated to the lungs, which were documented by new elevation of serum beta-HCG levels and computed tomographic scans despite continuing with 3 more cycles of chemotherapy. The patient died 6 months after diagnosis.