To determine the prevalence and natural history of gastric varices, we prospectively studied 568 patients (393 bleeders and 175 nonbleeders) with portal hypertension (cirrhosis in 301 patients, noncirrhotic portal fibrosis in 115 patients, extrahepatic portal vein obstruction in 117 patients and hepatic venous outflow obstruction in 35 patients). Primary (present at initial examination) gastric varices were seen in 114 (20%) patients more were present in bleeders than in nonbleeders (27% vs. 4%, respectively; p < 0.001). Secondary (occurring after obliteration of esophageal varices) gastric varices developed in 33 (9%) patients during follow-up of 24.6 ± 5.3 mo. Gastric varices (compared with esophageal varices) bled in significantly fewer patients (25% vs. 64%, respectively). Gastric varices had a lower bleeding risk factor than did esophageal varices (2.0 ± 0.5 vs. 4.3 ± 0.4, respectively) but bled more severely (4.8 ± 0.6 vs. 2.9 ± 0.3 transfusion units per patient, respectively). Once a varix bled, mortality was more likely (45%) in gastric varix patients. Gastric varices were classified as gastroesophageal or isolated gastric varices. Type 1 gastroesophageal varices (lesser curve varices) were the most common (75%). After obliteration of esophageal varices, type 1 gastroesophageal varices disappeared in 59% of pateints and persisted in the remainder; bleeding from perisistent gastroesophageal varices was more common than it was from gastroesophageal varices that were obliterated (28% vs. 2%, respectively; p < 0.001). Type 2 gastroesophageal varices, which extend to greater curvature, bled often (55%) and were associated with high mortality. Type 1 isolated gastric varices patients had only fundal varices, with a high (78%) incidence of bleeding. Type 2 isolated gastric varices were mainly (86%) ectopic, secondary gastric varices that bled only rarely (9%). Sclerotherapy was more effective in controlling acute bleeding and obliterating varices in gastroesophagael varices than in isolated gastric varices; the latter often required surgery. In conclusion, gastric varices are a common and serious complication of portal hypertension. Our classification was helpful in understanding the natural history and management of gastric varices.