The OMG’s Model Driven Architecture (MDA) is an ambitious effort to build programs from models using model transformations. In this article, Martin Fowler shares his concerns about MDA. Many have tried to build rich, comprehensive, unified models and languages. In each case, they were well motivated, basing their models on leading edge ideas. However, these models were unsuccessful due to their complexity and the rapid rate of change in the industry. MDA, as currently defined and espoused, will likely meet the same fate. However, used in moderation and where appropriate, UML and MDA code generators are useful tools, although not the panaceas that some would have us believe.