Human exposure to environmentally released biotechnology agents may occur. Therefore, it is important to identify adverse health effects associated with this exposure. The study investigates colonization, competition, and translocation of biotechnology agents following intranasal challenge by sublethal doses of the environmental isolates Pseudomonas maltophilia (BC6) and Pseudomonas aeruginosa (BC16, BC17, BC18, AC869). Two clinical Pseudomonas aeruginosa isolates (PAO1, DG1), are included for comparison. Following intranasal challenge by approximately 10 to the sixth power colony-forming units (cfu), recovery of the dosed strains were determined in C3H/HeJ mice at time intervals in the intestinal tract, mesenteric lymph node (MLN) complex, liver, and spleen. Intestinal bacterial populations also were enumerated. Strains BC6, AC869, DG1, and PAO1 were detectable in all three intestinal region 14 d following treatment. Strain BC17 was cleared 7 d posttreatment. Strains BC18 and BC16 were detectable in two of the three intestinal sections. A decrease in cecal lactose nonfermenting enteric bacilli was detected in strain BC6-treated mice. Translocation of strains BC16, AC869, and PAO1 occurred to the MLN, spleen, and liver. Strain BC18 was detectable in the liver, and strains of BC17 and DG1 were recovered from both the MLN and the liver. Pulmonary challenge can result in intestinal survival, competition and translocation.