The NASA balloon program research and development (R&D) efforts have focused on the development of technologies to support increased capability balloon missions. Advances made in analytical structural/performance modeling and light-weight composite materials offered the promise of superpressure balloons capable of extended flight duration. Experience with the NASA long duration balloon (LDB) systems have demonstrated the ability to send and receive scientific data and control missions on a global basis for up to approximately 20 days. It appeared that scientific ballooning was ready for the next step in capability. In 1997 a project was approved to develop and demonstrate those technologies required to support balloon missions lasting up to 100 days above 33.5 kms. The development project, called the ultra long duration balloon project (ULDB), will conclude with a demonstration flight in the year 2000. The ULDB project consists of four major systems: vehicle and recovery, ballooncraft, mission and operations, and science instrument. Technical challenges include the balloon materials, fabrication, power, thermal control, attitude control, telecommunications, data storage and international overflight. An overview of the ULDB project will be presented which addresses requirements, technical challenges, development activities, results and status of the ULDB project.