The objectives of this study were to investigate the effectiveness of buffer strips for the protection of receiving waters from deterioration following forestry activities such as ploughing and fertilization, and to make practical recommendations concerning optimum buffer strip width for use by forestry and water regulatory staff. The study was undertaken at an upland site near Dalmellington, Scotland, with full collaboration from the Forestry Authority's research division at Wrecclesham and the local district office at Straiton. Two test sites were chosen, one with mineral and the other with peat soils. The effects of the buffer strips on runoff quality were assessed by manual sampling and analysis at intervals down the strips, and using in situ suspended solids monitors. Flow rates were also recorded continuously. The study demonstrated that the effects on runoff water quality of ploughing peat were short lived compared to that for mineral soils, and that the main mechanism by which the buffer scrip effects an improvement on runoff quality is through settlement of particulate material. The factors that control this are velocity of flow, slope, distance travelled, lateral dispersion and the type and nature of the buffer strip vegetation. The vegetation reduces flow velocity and encourages dispersion but the effect declines as the vegetation decays and is flattened by successive winter runoff.