In plants, gametes are formed in multicellular haploid structures, termed gametophytes. The female gametophyte of most higher plants comprises seven cells, which develop from a single haploid spore through nuclear proliferation and subsequent cellularization. The female gametophytic cells differentiate into four distinct cell types, which play specific roles during fertilization and seed formation thereby ensuring reproductive success. In recent years many new techniques and cell type-specific marker lines have been established, making the female gametophyte an attractive system to study mechanisms of reproduction as well as cell specification. The following chapter describes a basic protocol for, first of all, recognizing a female gametophytic mutant and subsequently analyzing the phenotype on a morphological, molecular, and functional level.