This paper presents a survey of significant developments in research on the leaching of oil paint films by organic solvents, from the first systematic investigations carried out in the 1950s to more recent “clinical” studies involving the sampling and analysis of paintings during treatment. Key studies are discussed in the context of an improved knowledge of oil paint chemistry that has developed in recent decades and advances in analytical techniques that have allowed a more informed and precise analysis of the solvent-extractable components of aged oil paints. Current research related to solvent cleaning effects, including studies of the formation of metal soaps and their migration in oil paints and the leaching effects of aqueous cleaning systems on acrylic paint media, is considered. The challenges of interpreting experimental data in relation to cleaning practice are outlined and illustrated with reference to discussions of research on solvent effects in the conservation literature.