The CFHTLS Deep survey covers 4 square-degrees spread over 4 uncorrelated areas of the sky. Each patch covers about 1x1 square degrees and is located far from the galactic plane, in order to minimise galactic exctinction and bright star contamination. They will all be observed in u,g,r,i and z band, with exposure time of 33hrs in u, 33 hrs in g, 66hrs in r, 132hrs in i and 66hrs in z.

Main scientific goals : evolution of galaxy clustering in the universe, very distant quasars and very distant clusters of galaxies and star formation history of most distant galaxies. The Deep survey will accumulate the SNIa exposures over the next 5 years in order to produce 4 fields as deep as the Hubble Deep Field, but covering a field of view 3500 larger.