The foaming behaviour of the anionic surfactant Sodium Dodecyl Sulphate (SDS) has been studied in the presence and in the absence of the nonionic polymer Poly Vinyl Pyrrolidone (PVP). A current model of surfactant - polymer aggregation in bulk and at the air-water interface is related to the foam and thin film stability. Tensiometry, foaming tests and a thin film balance are used to obtain this relationship. It is found that at very low surfactant concentrations, where the surfactants are present as unimers in the bulk solution, there is association between surfactants and polymer at the liquid/air surface, giving an increased foam and thin film stability as compared to the same surfactant concentration but without polymer. As the surfactants and polymers associate in the bulk solution there is desorption of surfactants and polymers from the surface rendering a decrease in foam and thin film stability. At higher surfactant concentrations the bulk viscosity is significantly increased due to the presence of both micelles and saturated micelle-polymer complexes. Also the surfactant surface coverage at the liquid/air surface has reached its maximum value and is similar to the SDS solution above the CMC when no polymer is present. Both the increased surface viscosity and the increased bulk viscosity contribute to the observed foam and film stability. In the thin film studies several stratification steps are observed probably due to micelles, which are being pushed out of the film.