In cytological evaluation of cells, the nuclear characteristics present significant opportunities for early detection of abnormalities arising from various types of cancer. Accurate representation of cell nuclear structure by traditional manual inspection is difficult and time-consuming. In this paper, we introduce a new semi-automated cell segmentation algorithm combining a histogram-based global approach with local watershed segmentation. The procedure requires very little prior knowledge or user interaction. Preliminary results of accurate segmentation of the nucleus from the cell are presented to demonstrate potential application of this algorithm in cytological evaluation of abnormal nuclear structure.