Myb2, which regulates iron inducible transcription of the ap65-1 gene in the protozoan parasite Trichomonas vaginalis, was persistently detected in the nucleus. In the study, the nuclear localization signal of Myb2 was investgated exploiting immuneflouorescence assay to monitor subcellular localization of Myb2 and its mutant proteins. The region 48-143 was found to be sufficient, while 55EEDE58 as well as anyone of the structure elements in the R2R3 DNA-binding domain to be essential for nuclear import. Moreover, 51KF52, 139NRW141, and 143T/S145 together may also play important roles in Myb2 nuclear import. As examined by Western blotting, the region spanning 144-179 may contain a site for post-translational modification, which is not required for Myb2 nuclear import. Signal transduction pathway involve in Myb2 nuclear import were not identified. These observations suggest that Myb2 nuclear translocation is controlled by a novel nuclear localization signal.