This paper offers and tests a model for national union adoption of information technology (IT). Data come from a mail survey of national unions that were active in the U.S. in 1997. Consistent with the model's predictions and prior research on union innovation, results indicate that rationalization and size are key predictors of IT adoption. Results also suggest a role for decentralization, employer use of information technology, and prior innovation. IT adoption may be one of the most important areas of union innovation in decades, and may have substantial impacts on union outcomes and possibly on the nature of unions. Understanding the nature and causes of IT adoption by unions may provide insight on the changing nature of unions and their roles in the future.