The HCS LipidTOX™ Green phospholipidosis detection reagent was developed to characterize the potentially toxic side effects of compounds on lipid metabolism in mammalian cell lines. This reagent is easily detected by fluorescence microscopy or an HCS reader equipped with filters that can detect excitation/emission maxima ∼495/525 nm. LipidTOX™ phospholipidosis detection reagents do not affect the normal growth of cells, and the staining observed after incubation in live cells is maintained after formaldehyde fixation. This probe is compatible with the HCS LipidTOX™ neutral lipid stains (H34475, H34476, and H34477).