The orthorhombicity within the the layers of high Tc cuprates naturally introduces anisotropy in the electron interaction. This anisotropy creates a d+s pairing in the weak-coupling limit and for a cylindrical Fermi surface, enhancements of Tc and Δ(0)/Tc, the appearance of two neighboring peaks in the density of states and an a−b anisotropy in the upper critical field Hc2. In the presence of nonmagnetic impurities and in the vicinity of the critical concentration where Tc vanishes, there is a gap opening in the d+s case showing a tendency to become more s like. The low temperature thermal conductivity reflects this anomaly and also exhibits an a−b anisotropy. These features should be testable.