Numerous lymphoblastoid cell lines (LCLs) which secreted antibodies against Pseudomonas aeruginosa (all Fisher's immunotypes and Homma's immunotype 1) were established by Epstein-Barr virus (EBV)-transformation of lymphocytes. Five LCLs were established as long-term culture lines and their properties were determined. These LCLs produced monoclonal antibodies to Fisher's immunotype 1 and 4 and Homma's immunotype 1, and their immunoglobulin classes were IgM, IgG, and IgA. We found that three monoclonal antibodies (G3-1, H7-2, and E10-1) among them successfully protected mice from the corresponding immunotype of P. aeruginosa infection. Their protective dose (PD50) values were 0.5, 2.6, and 3.1 micrograms immunoglobulin/mouse. These human monoclonal antibodies against P. aeruginosa prepared by EBV-transformation method will be a valuable aid for the treatment for severe P. aeruginosa infections.