The main goal of this work is to prove that a very generic surface of degre
e at least 21 in complex projective 3-dimensional space is hyperbolic in th
e sense of Kobayashi. This means that every entire holomorphic map f: C -->
X to the surface is constant. In 1970, Kobayashi conjectured more generall
y that a (very) generic hypersurface of sufficiently high degree in project
ive space is hyperbolic. Our technique follows the stream of ideas initiate
d by Green and Griffiths in 1979, which consists of considering jet differe
ntials and their associated base loci. However, a key ingredient is the use
of a different kind of jet bundle, namely the "Semple jet bundles" previou
sly studied by the first named author. The base locus calculation is achiev
ed through a sequence of Riemann-Roch formulas combined with a suitable gen
eric vanishing theorem for order 2-jets. Our method covers the case of surf
aces of general type with Picard group Z and (13 + 12 theta(2))c(1)(2) - 9(
c2) > 0, where theta(2) is the "2-jet threshold" (bounded below by -1/6 for
surfaces in P-3). The final conclusion is obtained by using recent results
of McQuillan on holomorphic foliations.