The breakup of an elongated drop in the presence of a centrifugal field was studied. The system used was a phase-separated colloid-polymer suspension; the elongated drop consisted of the lighter polymer-rich fluid phase and the surrounding fluid was its coexisting colloid-rich fluid phase. We found that the growth rate of the fastest growing disturbance of the drop, which eventually leads to its break-up, is decreasing upon an increase of the rotational speed, whereas the wavelength of the disturbance is increasing upon an increase of the rotational speed. We present a simple analysis of the effect of the centrifugal field which accounts quantitatively for these features. Furthermore, this analysis allows for the determination of the interfacial tension from the measured growth rates.