Objectives: This study aimed to evaluate the incidence and the time course of methotrexate (MTX)-associated gastric intolerance in patients with rheumatoid arthritis and psoriatic arthritis. Methods: Four hundred twenty subjects undergoing MTX treatment for rheumatoid arthritis (n = 346) and psoriatic arthritis (n = 74) were retrospectively assessed. The incidence and time course of gastric MTX intolerance resulting in treatment discontinuation were investigated. In addition, the relations between gastric intolerance and patient characteristics, including gender, age, diagnosis, and rheumatoid factor (RF) positivity, were examined. Results: Overall, oral MTX discontinuation rate due to gastric intolerance was 28.6 %. The time to discontinuation for oral MTX was 8.1 ± 11.5 months on average, with more than half of the discontinuations occurring within the first three months of treatment. Discontinuation was not associated with gender, age, diagnosis, or RF positivity. More than half of the patients that switched to a parenteral treatment regimen (52.6 %, 20/38) could tolerate the agent. Conclusions: Gastric MTX intolerance usually develops within the first year of treatment and presents a major obstacle to long-term treatment retention in patients with rheumatologic disease. However, parenteral MTX appears to be a good alternative for patients intolerant of oral MTX. © 2012 Japan College of Rheumatology.