Static light scattering may be used to probe the solution behavior of complexes of integral membrane proteins with detergents. As has been observed with soluble proteins, the crystallization behavior of protein detergent complexes can be reliably predicted by the second osmotic virial coefficient (B-22), which is obtained from light scattering. Conditions which yield crystals map to a narrow window of B-22 values falling within the "crystallization slot" previously described for soluble proteins. This slot ties near the cloud point of the detergent used for crystallization. The detergent portion of the protein-detergent complex appears to be an important factor in determining the B-22 values for the complex. This suggests a strategy for the design of membrane protein crystallization screens which focuses principally on optimization of detergent-detergent interactions. Cloud point assays have been developed to facilitate collection of the data necessary to construct such screens.