During the past year, I took the first steps in developing Francisella tularensis into a useful model of bacterial pathogenesis. I attempted to introduce exogenous DNA into Francisella using a variety of methods, and succeeded by transforming recombinant clones containing transposon insertions. The recombinant clones apparently integrated into the chromosome, thus preparing the way for gene replacement studies. I have also cloned the genes encoding five presumptive outer membrane proteins. One of the clones expresses a heat and 2-mercaptoethanol modifiable protein. This protein, FopA, is one of the major immunogens seen in Francisella infections.