Bacterial cancer caused by Clavibacter michiganensis ssp. michiganensis is one of the most serious tomato diseases, inducing substantial economic losses worldwide. It is a quarantine organism in European Union and in several other countries. There is no efficient suppression and no resistant tomato variety found. The detection of Clavibacter michiganensis ssp. michiganensis is not always possible especially on tomatoseedlings. This slow-growing pathogen is hard to see, symptoms only appearing as plants approach maturity. Obviously very low level of bacteria is hard to detect with common ELISA test , so in this tests of detection improvement, intention was to raise bacteria concentration at least to threshold of common ELISA test. For a start, tomatoseedlings were inoculated with different bacteria dilutions. They were average 30 cm height (DC 23). The plants were inoculated by stabbing the stem at the height approximately 10 cm. Following, leaves and stems were tested separately. Results by leaves were always negative even by control dilution which was highest in this tests (8x108 cfu/ml) but results by stems were all positiv. Therefore, for following tests only stems of tomatoseedlings were used. The experiments were based on 3 methods, alone or among each other, to enrich bacteria concentration in plant sap. For example to incubate at 20 and 26 C, to filter or to centrifuge. As control, served direct test on plant sap from artificial inoculated plant. Samples for detection with ELISA Test were taken exact on 3, 5 and 7 days after infection. From all variants, by lowest used bacteria dilution 1,2 x 10 cfu/ml, even 3 days after infection following variants were positiv on ELISA test: incubated plant sap at 20 ( 16 hours), filtrate of plant sap also incubated at 20 ( 16 hours), filtrate + centrifugate at 20 ( 16 hours) as well as simply centrifugate incubated at 20 ( 16 hours). Therewith, bacteria reproduction was increased so that they could be detected by ELISA. In addition, Clavibacter michiganensis ssp. michiganensis was successfully detected with PCR, direct from young plants about 30 cm height (DC 23). Favorable method to test tomatoseedlings represents ELISA testing method.