In the absence of spindle MTs, RPE-1 cells spend 20–30 h in mitosis. Images from video records of cells entering and exiting mitosis in 3.2 μM nocodazole (A), 250 nM colcemid (B), 25 nM vinblastine (C), or 1 μM vinblastine (D). In each sequence, the second frame defines the start of mitosis, the third the end, and the last depicts the chromosome (DNA) and MT pattern in a mitotic cell from a similarly treated culture fixed and stained for the immunofluorescence localization of MTs. Time from addition of the drug to the medium is in minutes. Arrows note the cell that is followed in subsequent frames. Bars: (IMF images) 5 μm; (phase images) 20 μm.