Significant research effort has focussed in recent years on identifying natural and environmentally friendly sources of antimicrobial agents, for applications in agriculture as well as human health. This quest has led to identification of a number of small, cysteine-rich, and typically basic proteins which have antibacterial and antifungal activities. These include the non-specific lipid transfer proteins (ns-LTPs), puroindolines (PINs), and thionins. Extensive biochemical studies have shown higher order structures as well as specific residues and/or domains to be important for membrane activities. Numerous in-vitro tests have confirmed their antibacterial and/or antifungal activities, some studies showing variations in their growth inhibitory concentrations or strain specificities. Transgenic transfers of the respective genes into diverse backgrounds have also led to successful in-planta expression and enhanced microbial defence. The ns-LTPs, PINs and thionins thus make excellent candidates as biocontrol agents of plant pathogens.