Plant tumors, including genetic tumors, are disorganized and proliferate in an uncontrolled fashion. In this report we describe the morphological, physiological and genetic properties of Nicotiana. langsdorffii and Nicotiana. glauca and their hybrids (Nicotiana. langsdorffii x Nicotiana. Glauca). Nicotiana. langsdorffii leaves are oblate and pubescent with winged petioles, while Nicotiana. glauca leaf-blades are rubbery and oval-to-heart-shaped. The hybrid plants are intermediate in leaf shape, with anisocytic stomata and well-developed trichomes. In addition, they produce tumors in the absence of bacteria and exogenous hormones. Tumor growth in the hybrid plants was not affected by indole-3-acetic acid or kinetin. Genetic polymorphism was analyzed by the randomly amplified polymorphic DNA technique in the parents (Nicotiana. langsdorffii and Nicotiana. glauca) and in the genetic tumors produced by the hybrids. A total of 128 randomly amplified polymorphic DNA fragments were scored from fifteen random primers, and pronounced differences were found between the genetic tumors and their parents. These observations show that randomly amplified polymorphic DNA markers are might informative about genetic similarities and dissimilarities