AbstractFlow cytometric perpendicular and forward light scatters have been employed to evaluate whether the changes in chromatin organization due to ionic strength, Mg++concentration and pH, visible in electron microscopy, can be monitored by flow cytometry.The average intensity of the perpendicular light scatter signal increased as nuclear chromatin became decondensed by lowering the ionic strength or releasing H1 histone at low pH values.These results indicate that flow cytometry signals and in particular the perpendicular light scatter allow the detection of the conformational transitions in chromatin and may therefore be useful for studying cell cycle associated morphological changes in isolated nuclei.