Continuous renal replacement therapy (CRRT) is a relatively new extracorporeal blood purification modality that is rapidly gaining acceptance for the treatment of acute kidney injury in cats and dogs. The author has used CRRT for the treatment of leptospirosis, tumor lysis syndrome, heatstroke, pre- and postsurgical support of ureteral obstructions, as well as aminoglycoside and melamine toxicities. As the name implies, CRRT is a slow gradual process, and once treatment begins, patients continue therapy until their renal function returns, they are transitioned to intermittent hemodialysis (IHD), or they are euthanized. Unlike IHD, which is a primarily diffusive therapy, CRRT uses diffusion as well as convection. Because of its efficient use of fluids, CRRT units use prepackaged fluids, eliminating the need for costly water purification systems that are needed for IHD.