In contrast to nematics far less is known about the alignment of the directors in a smectic A phase by an external field. To characterise this process, which necessarily involves the flow of the molecules, we have undertaken an NMR investigation of the smectic A phase of 4-octyl-4′-cyanobiphenyl. The results of these experiments have revealed that, as expected, the alignment of the directors is a complex process strongly influenced by the nature of the containing surface for the smectic A phase. To assist in understanding the alignment process we have used computer simulations to study the field induced alignment of the directors in the smectic A phase formed by the Gay-Berne mesogen GB(4.4,20.0,1,1).