Six chromosomal transposon mutations in Agrobacterium tumefaciens which result in an inability to synthesize cellulose fibrils were mapped to the vicinity of trp-2 and met-6. Mutations which result in an inability to attach to plant cells, attC43 and attC69, also mapped in this region, as did one Tn5 mutation which caused overproduction of cellulose. Another cellulose overproduction mutation mapped at a distance and was closely linked to ilv-13. The results suggest that there is a region of the A. tumefaciens chromosome located near met-6 which is concerned with the interaction of the bacterium with the host cell surface.