The force-displacement curves for the penetration of a commercial shaving cream foam by a vertical circular cylinder were obtained using a very sensitive tensile machine. From these results, the (apparent) viscosity, mu, of the foam was calculated. The effects of the velocity of indentation, of the radius of the indenter and of the radius of the cylindrical vessel which contains the foam were experimentally studied. A theoretical analysis of foam indentation was undertaken under the assumption that the foam behaves as a power-law fluid; i.e., the foam viscosity, mu, has a power dependence on shear rate, gamma, with mu proportional to gamma ((n-1)). This hypothesis describes well the experimental results and the power law exponent found was n=0.56.