The criteria for selecting effective solvent systems for wet development of polymer resist materials are explored. Methods of estimating the polymer–solvent interactions are described, including the use of solubility parameters and the Flory–huggins interaction parameter. Methods of achieving θ-conditions, which represent minimal solvent–precipitant mixtures, or the more novel approach of establishing cosolvent systems are described. The rate dissolution has also bee identified as a controlling parameter. Some optical and gravimetric methods for measuring dissolution rates for polymer films are outlined. Examples of the influence of these factors on the sensitivity and contrast of resists such as poly(methylmethacrylate) and poly(p-methyl styrene-stat-chloromethyl styrene) are described.