Characteristics are described of small-colony variants of Xanthomonas campestris NRRL B-1459 which are frequently encountered when routine culture maintenance procedures are employed. In contrast to the parental type, smallcolony variants were shown to be resistant to a number of antibiotics, to acridine orange, and to phage which are virulent for the parent colony type. Sensitivity to ultraviolet radiation was similar in both colony types. A simple method for preservation of viable cells is described. The suitability of the method for providing reproducible inocula free from variant cell types is examined.