Protein dielectrophoresis (DEP) has the potential to play an important role as a manipulation, fractionation, preconcentration, and separation method in bioanalysis and as manipulation tool for nanotechnological applications. The first demonstrations of protein DEP have been reported almost 20 years ago. Since then various experimental realizations to manipulate proteins by DEP as well as more targeted applications employing protein DEP have been demonstrated. This review summarizes the experimental studies in the field of protein DEP trapping and focusing as well as specific applications in separation, molecular patterning, on bioprobes and biosensors. While a comprehensive theoretical model describing protein DEP is still lacking we also attempt to provide an overview of the factors influencing protein DEP and relate to currently available theoretical models. We further point out the variations in experimental conditions used in the past to study the somewhat 20 proteins as well as the implications of protein molecular structure to the DEP response.