The surface rheological behaviour of spread monolayers of DPPC (L-alpha-dipalmitoyl phosphatidyl chinoline) and DMPE (L-alpha-dimyristoyl phosphatidyl ethanolamine) on water has been investigated under shear and dilation/compression deformation. Harmonic area perturbations are performed using an oscillating barrier method which provides information on the monolayer dilational elasticity and the relaxation processes happening in the monolayers as a function of surface pressure. A surface shear rheometer has been used to measure the surface shear viscosity and elasticity of the same monolayers. The shear and dilational rheological properties can be explained by the morphology of the phospholipid monolayers as a function of surface pressure.