ABSTRACT
A total of 770 rodents (40 rats, 100 hamsters and 630 rodents) were serologicall examined in the old natural foci in some of the Eastern Slovakia regions; there were 10.6% of positive reactions to Leptospirosis in dilutions ranging from 1 : 100 to 1 : 1600. In rats 17 sers (40%) proved to be positive to leptospira, mostly reacting with the L. icterohaemorrhagiae. A positive reaction with the leptospira antigen was found in 13 sera (15%) of hamsters; the sera reacted with the Leptospira grypposa more frequently than with the L. serjoe. In the group of small rodents the greatest number of positive reactions to leptospirosis was obtained in microtus arvalis (10.7%); the sera reacted most frequently with L. grippotyphosa and L. serjoe. As many as 9 serological types were revealed in the group examined.