Small angle neutron scattering (SANS) is a powerful tool for studying the structure of solubilized membrane proteins. It allows describing the general dimension of the membrane protein , evidence conformational changes, and may provide a low-resolution structure at the nm resolution range. This is because SANS can discriminate between the membrane protein and its amphiphilic partner by specific deuteration of the partners and of the buffer. This chapter was written to offer to a scientist aiming to describe a membrane protein structure the basic tools to consider a SANS experiment. It presents the general principle of contrast variation and a bibliographic survey of experimental strategies used for membrane proteins, some basic theoretical background, and a succinct description of the principles of analysis, of the instrumental and sample requirement, and of the practical steps, prior to the experiments, during the experiments and for data analysis.