A rabbit antibody to bovine brain MAP 1C was prepared. The antibody stained the mitotic spindle of PtK2 cells by immunofluorescence. On immunoblots of PtK2 cell extract the antibody reacted with polypeptides of molecular weights greater than 350 and 80 KD that resemble the subunit proteins of bovine brain MAP 1C. An additional 135 KD polypeptide in the extract was also stained. These results indicate that a cytoplasmic dynein recognizable by the anti-MAP 1C antibody is localized in the mitotic spindle.