Lamina-associated polypeptide (LAP) 2, which directly interacts with B-type lamins and chromosomes, is an integral membrane protein specifically distributed along the inner nuclear membrane of the nuclear envelope. The chromatin- and lamin-binding activity of LAP2 suggests that LAP2 plays an important role in targeting mitotic vesicles to chromosomes and reorganizing the nuclear structure at the end of mitosis. Here I identified a LAP2 interacting protein, termed L2BP1 (LAP2 binding protein 1). The rat L2BP1 cDNA sequence is predicted to encode a protein of 89 amino acids which turns out to be a rat homolog of mouse and human BAF (Barrier-to-Autointegration Factor). L2BP1 is distributed diffusely throughout the nucleus in interphase cells. It is, however, highly concentrated at the chromosomes during the M-phase. Further, the L2BP1 binding domain of LAP2 overlaps its chromosome-binding region. These findings suggest that L2BP1 is a candidate mediator of LAP2-chromosome interaction at the end of mitosis.