Six proteinase inhibitors have been isolated from a crude inhibitor preparation from Phaseolus vulgaris var. nanus (bush bean: Borlotto) by gel chromatography and ion exchange chromatography. The isoelectric points of the inhibitors are between 4.35 and 5.65. The molecular weights of the inhibitors PVI-2, -3(1), -3(2), and -4 and between 8000 and 9500. The C-terminal and N-terminal amino acid residues and the amino acid compositions of these four inhibitors are given. The inhibitors PVI-1, -2, -3(1), -3(2), -4, and 5(1) all inhibit trypsin and with the exception of PVI-3(1) also alpha-chymotrypsin. PVI-3(1) inhibit elastase. The inhibitor mixture, PVI-G, exhibits a weak inhibition of some microbial serine proteinases. Some other endopeptidases and exopeptidases tested are not inhibited. Crude inhibitor preparations from P. coccineus and Pisum sativum show the same behaviour.