During the period 1984-86 the symptoms of an unusual, previously unknown disease were observed on sunflower hybrids and a variety in different parts of the country. Soft rot symptoms appeared on stalks, petioles and heads. The frequency and severity of the disease varied greatly on the different organs and areas It was presumed, that a bacterium is the causal agent of the disease. Isolations were performed and biochemical tests carried out. The identification procedure including artificial inoculation tests proved, that two Erwinia carotovora subspecies, namely E.c. subsp. carotovora and E.c. subsp. atroseptica are present which are able to infect sunflower causing a severe disease and loss of yield. Evaluating the behaviour of inbred materials and commercial hybrids under natural infection conditions, it can be stated that there are remarkable differences in resistance of the genotypes tested. This phenomenon can be a basis for breeding for resistance as an effective means of control ling this destructive disease.