CArG box‐binding factor‐A (CBF‐A) is a protein involved in transcriptional control and interacts specifically with the penta‐decameric (pd) element in κ promoters. We show here that CBF‐A will also bind specifically to a second region in the κ promoter that overlaps with an early B cell factor binding site. Furthermore, the same region is present in multiple Ig promoters and we show that CBF‐A can bind to several of these. Mitogenic stimulation of untransformed B lymphocytes promoted nuclear localisation of CBF‐A. Using enhanced GFP (EGFP)‐tagged constructs and transfection into COS7 cells, a nuclear localisation signal was defined in the C terminus of CBF‐A. Deletion of only 13 amino acids from the C terminus of CBF‐A led to the accumulation of the protein in bright speckles at the nuclear/cytoplasmic border. We also identified the heterogeneous ribonucleoprotein H as a specific interaction partner of CBF‐A, but this interaction could be detected in the cytoplasm only. Thus, CBF‐A has the potential to regulate the expression of multiple Ig V genes and has a complex, mitogen‐responsive regulation of its intracellular localisation.