The presence of koi carp herpesvirus (KHV) infection in Poland was confirmed in common carp reared for consumption. Virus was isolated in CCB cells using cocultivation technique. The carps were experimentally infected and virus was reisolated and identified with PCR method. Monitoring of KHV in 15 carp farms showed the presence of the virus in 4 farms. We have found that lowering of the water temperature to 11-12 degrees C could eventually provoked the recurrence of the disease symptoms in latently infected survivor carp, and thus could help to detect KHV with PCR or co-cultivation methods. Analysis of sequencing data of 484 bp fragments of KHV DNA of 4 Polish isolates revealed the complete identity in 3 cases. One of the Polish isolate differed from the remaining 3 variants by 5 nucleotide substitutions. In order to evaluate fully the importance of small differences in DNA sequences of the KHV isolates, corresponding amino-acid analysis, and subsequent virulence studies are necessary.