Summary: We present a web-server for rapid prediction of changes in protein stabilities over a range of temperatures and experimental conditions upon single- or multiple-point substitutions of charged residues. Potential mutants are identified by a charge-shuffling procedure while the stability changes (i.e. an unfolding curve) are predicted employing an ensemble-based statistical-mechanical model. We expect this server to be a simple yet detailed tool for engineering stabilities, identifying electrostatically frustrated residues, generating local stability maps and in constructing fitness landscapes. Availability and implementation: The web-server is freely available at http://pbl.biotech.iitm.ac.in/pStab and supports recent versions of all major browsers. Contact: [email protected]. Supplementary information: Supplementary data are available at Bioinformatics online.