  We consider the three-dimensional Ising model slightly below its critical
temperature, with boundary conditions leading to the presence of an interface.
We show how the interfacial properties can be deduced starting from the
particle modes of the underlying field theory. The product of the surface
tension and the correlation length yields the particle density along the string
whose propagation spans the interface. We also determine the order parameter
and energy density profiles across the interface, and show that they are in
complete agreement with Monte Carlo simulations that we perform.
