Kidney function investigations in veterinary medicine are traditionally based on blood analysis (bloodurea nitrogen (BUN) and serum creatinine concentration) and / or urinalysis (urine specific gravity, proteinto-creatinine ratio or fractional excretion). Morphologic information is usually obtained by abdominalradiography or ultrasonography. However, when more specific information on the functionality of the kidneysis needed, nuclear medicine offers various tracers that specifically represent glomerular filtration rate, effectiverenal plasma flow or functional renal mass, sometimes combining functional and morphologic data. Theseprocedures can be based on blood sampling techniques (non-imaging methods), or data can be obtained usinga gamma-camera (imaging methods). The most commonly used radionuclides for the examination of kidneyfunction in small animal medicine are discussed in this review.