The influence of the Ca++and inhibitor concentrations, pH, and temperature on the phase behaviour and precipitation yield of a phosphinopolyacrylate scale inhibitor, PPAA, has been studied. The results are interpreted in terms of the chemical processes governing PPAA-Ca++complexation, and evidence for the role of inhibitor molecular weight in determining the degree of precipitation is produced. Comparative adsorption and precipitation squeezes, carried out in sandpacks, demonstrate that significant enhancement of the treatment lifetime can be achieved when conditions giving extensive inhibitor precipitation are used. The sandpack experiments and dissolution studies on the precipitated inhibitor both suggest strongly that kinetic phenomena influence the return level of inhibitor in the field. Together these studies point the way to approaches for optimising inhibitor precipitation squeeze treatments in order to control scale deposition in petroleum reservoirs.