The objective of this experiment was to identify strains of the crown gall organism Agrobacterium that are virulent on cotton. The mechanism of pathogenicity resides in the ability of the bacterium to insert into plant cells via the Ti plasmid a fragment of DNA which of this mechanism is used in genetic engineering to insert foreign genes into plants. Our rationale was that the ability of a strain of bacterium to induce the ability to transform cotton cells. Coker 312 was selected because of its potential for plantlet regeneration from callus tissue. Seed were germinated in 3" pots containing an equal mix of sand, soil and vermiculite. Seedlings were irrigated with 1/10 modified Hoagland's solution as needed. After the first true leaf formed, the epicotyl was excised with a scalpel smeared in the Agrobacterium strain being tested. Two replications of three cotton seedlings each were inoculated for each of the fifteen strains tested Tumors were allowed to develop on the stump for 6 weeks and any cotyledonary buds which grew were removed during this time. The tumors were scored and categorized as >5mm, between 0 and 5mm, and 0. With this technique 5 Agrobacterium strains were identified as being virulent on Coker 312, 4 caused moderated tumor response and 6 induced no response. The virulent strains will be used in other experiments designed to establish and efficient transformation system for cotton.