The chromosomal location of the transformation suppressor gene KREV1 and its pseudogene (KREV1P) on R-banded human prometaphase chromosomes was determined by fluorescence in situ hybridization. The KREV1 gene mapped to chromosome 1p13.3, whereas the KREV1P pseudogene mapped to 14q24.3. Our results substantiate the previous mapping data of Rousseau-Merck et al. (1990) and further confine the position of the RAP1A/KREV1 gene to a narrower region.