Kidneys regulate the excretion and homeostasis of water and solutes. They are also metabolically active organs and possess the ability to actively concentrate certain substances and metabolically activate or biotransform a variety of xenobiotic compounds. In vitro techniques discuss isolated perfused kidneys (IPK). The great discoveries in renal physiology, pharmacology, and toxicology have been carried out in renal slices. Most toxicological studies utilizing slices have been done with those from the cortex because of the importance of proximal tubule transporters in renal toxicology. Isolated glomeruli, tubule segments and cells are described. In this model the cells or nephron segments are separated from each other with a minimum of damage and subsequently enriching the sample in the desired cell type. Isolation of single cell suspension is discussed. This process requires more vigorous enzyme treatment as compared to isolation of nephron segments as the cells must be separated from each other and released from the extracellular matrix and basement. Simple collagenase digestion protocol is explained. Coronal slices are used to dissect nephron segments from the medulla or from medullary rays. Glomeruli can also be eliminated from a tubule suspension by perfusion of the intact kidneys with a paramagnetic iron oxide solution. Cell cultures used in toxicology should maintain the differential characteristics of the original tissue in order to accurately reflect in vivo responses of target tissues to toxic chemicals. LLC-PK cells, OK cells, JTC-12 cells, MDCK cells, and A6 cells are discussed.