Phenotype MicroArrays (PM) are offered for cell-based assays used with mammalian cell lines. The mammalian cell capability is added to the expanding list of uses of PM technology for a variety of research applications including drug discovery, functional genomics, and cellular toxicology. PM technology has already been applied for use with a variety of microbial cells important in disease and industrial use, specifically bacteria, yeast and filamentous fungi. The PM mammalian cell panels also have broad utility. They have been optimized for use in a variety of human cell lines, including liver cell lines (HepG2, C3A), leukemia cell lines (CRF-CEM, HL60), a colon cancer line (Colo 205), a non-small cell lung cancer line (A549), a prostate cancer cell line (PC-3), a mouse cell line (TK-1) and non-immortalized mammalian cell lines. The first PM mammalian panels to be released provide 384 assays that probe different metabolic energy-producing pathways of cells. A second use of the mammalian panels is as a tool to fingerprint cell lines.