In this study we focused on expression pattern of a family of AHPs genes in different plant tissues. We also examined the influence of cytokinins on AHP gene expression. AHPs (Arabidopsis Histidine-phosphotransfer factors) are phosphotransfer shuttles in the multistep two-component system of signal transduction. AHPs transfer the phosphoryl group between membrane localised receptors (histidine kinases) and response regulators (transcription factors) localized in the nucleus. This system is thought to be involved in stress, cytokinin and ethylene signalling in Arabidopsis. Cytokinins have been implicated in developmental and growth processes in plants including cell division, shoot meristem initiation, senescence and germination. Five AHPs have been identified until now in Arabidopsis. AHPs are small proteins (14.5 18 kDa), with a predicted acidic isoeletric point (5.53.9) and a typical phosphotransfer domain, including the conserved sequence XHQXKGSSXS with the histidine residue binding the phosphoryl group. Using real time RT-PCR we characterized the expression pattern of AHP genes in adult wild type Arabidopsis thaliana (ecotype Columbia 0). Different plant organs were tested leaves, stems, roots, flowers and siliques. The influence of cytokinins on the level of AHP expression was tested on 8 day-old seedlings treated with the cytokinin benzyladenine (BA) and also on 8 day-old seedlings overproducing endogenous cytokinins. We show that the highest mRNA level of the AHP1 is in roots and highest level of AHP2 is in flowers, on the other hand there were no significant differences among tissues in expression patterns of AHP3 and AHP5. AHP4 was expressed at very low levels in all tissues tested but the highest level was found in leaves. Also most of tested AHPs have low relative expression in seedlings and siliques. A response to cytokinin was detected for AHP1 and AHP4, their steady-state mRNA levels going up. The expression of AHP3 was affected more by exogenous cytokinins and the AHP2 was more responsible to higher level of the endogenous cytokinins. Expression level AHP5 remains unaffected using cytokinins.