The marine gastropod Ilyanassa obsoleta is a long-standing and very useful model for studies of embryonic development. It is an especially important model for spiralian development, and for studies of asymmetric cell division. The embryos are amenable to classic embryological manipulation techniques as well as a growing number of molecular approaches. Ilyanassa is also an important model for studies of metamorphosis, the ecology of parasitism, the effects of environmental contaminants on morphology and sexual function, and comparative neurobiology. This protocol describes the procedure for extracting protein from Ilyanassa embryos for use in techniques such as Western blotting or two-dimensional (2D) gel electrophoresis.