Astronomy in the next decade will be dominated by multi-wavelength survey projects which address a wide variety of scientific issues, including galaxy formation and evolution, AGN structure and demographics, and Galactic structure. The extensive telescope facilities available to Chilean astronomers have offered us an excellent opportunity to conduct such a survey in the context of the Yale-Chile Joint Program.

The MUSYC (Multiwavelength Survey by Yale-Chile) project comprises about 1 square degree of sky imaged to AB depths of U,B,V,R=26.5 and K(AB)=22.5, with extensive follow-up spectroscopy. The survey covers four fields of 30'x30' each, chosen to leverage existing data and to enable flexible scheduling of observing time during the year. Each field will be imaged from the ground in the optical and near-infrared, and with space-based observatories in the optical (ACS on HST), X-rays (Chandra, XMM), and mid/far-infrared (SIRTF). Follow-up spectroscopy will be done mostly with multi-object spectrographs (VIMOS, IMACS, GMOS). The survey fields will be a natural choice for future observations with ALMA.

The survey is unique in its combination of depth and total area. The ``GOODS'' survey, for which hundreds of HST orbits, SIRTF hours, and ESO VLT hours are allocated, will yield an extremely deep view of two small areas of sky comprising a total of 0.08 square degrees. On the other hand, a myriad of ground based surveys cover several square degrees or more, to shallower depths of R~26 and K~20 and lack the full set of UBVRIz'JHK colors (examples are NOAO Deep/Wide, EIS Deep Public Survey, the Las Campanas Infra-Red Survey (LCIRS), and ESO's K20 survey). The Chile-Yale survey covers the ``middle ground'', with depth and area well matched to telescopes in space and ideally suited for efficient follow-up with multi-slit spectrographs.