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Notes: Several investigators1–4 have shown that burned animals are quite susceptible to systemic invasion by Pseudomonas aeruginosa. We have produced fatal septicemia in mice by immersion of the scalded tail (immersed in water at 70°C for five sec) in cultures of Pseudomonas strain 180. For purposes of local therapy the tails have been enclosed in rubber tubing held in place by stapling to the loose skin at the base of the tail (figure 1). Therapy consisted of suspending the drugs in a vanishing cream base and injecting the suspension into the tubes, which were then sealed with a cork. Treatment was given six hr after challenge. Details of the techniques employed may be found in recent publications.5,6In a comparative study of eleven chemotherapeutic agents, six were highly effective in preventing death. (See table 1). The mortality with 8.5% sulfamylon acetate was 8%; 0.25% chloramphenicol, 0.5% gentamycin, 0.4% neomycin, and 1% streptomycin all produced zero mortality; 0.5 sulfadiazine gave 10% mortality. Little effect on survival was observed from 0.2% polymyxin, 0.1% colimycin, 0.25% tetracycline, 0.25% penicillin G, or 0.5% silver nitrate. Ninetythree% of untreated animals died and 90% with the vanishing cream alone.5A similar study was carried out on mice treated systemically, and without local therapy. Treatment was begun six hr after the challenge and repeated once daily for four additional days. It was found that sulfadiazine given orally in doses of 100 to 500 mg/kg brought about complete survival, and streptomycin administered subcutaneously in doses of 100 mg/kg produced 90% survival (table 2). The drugs currently in use, polymyxin, colimycin, and gentamycin had little effect in the usual therapeutic doses.A comparison of in vivo activity with in vitro sensitivity revealed that test tube activity is not a reliable index of therapeutic action (table 3). Gentamycin, polymyxin, and colimycin were bacteriostatic at 1 μg per ml. Only gentamycin exhibited local activity, and colimycin was without effect systemically. Chloramphenicol, sulfadiazine, and streptomycin were equally active in vitro (25 μg/ml). All were effective locally, but systemically, chloramphenicol was inactive while sulfadiazine and streptomycin were most effective.