The genome sequence of Bacillus subtilis was published in 1997 and since then many other bacterial genomes have been sequenced, among them Bacillus licheniformis in 2004. B. subtilis and B. licheniformis are closely related and feature similar saprophytic lifestyles in the soil. Both species can secrete numerous proteins into the surrounding medium enabling them to use high-molecular-weight substances, which are abundant in soils, as nutrient sources. The availability of complete genome sequences allows for the prediction of the proteins containing signals for secretion into the extracellular milieu and also of the proteins which form the secretion machinery needed for protein translocation through the cytoplasmic membrane. To confirm the predicted subcellular localization of proteins, proteomics is the best choice. The extracellular proteomes of B. subtilis and B. licheniformis have been analyzed under different growth conditions allowing comparisons of the extracellular proteomes and conclusions regarding similarities and differences of the protein secretion mechanisms between the two species.