The kidney biopsy is an invaluable tool that has become the gold standard for the diagnosis of pathologic kidney diseases since the early 1950s. Throughout the years, immunohistologic and ultrastructural microscopy techniques have improved and provide more information on the cause and classification of kidney diseases than that available from simple light microscopy alone. Kidney biopsy has become a preferred method to obtain critical information that can be used in conjunction with serologic, urinary, and genetic testing to diagnose a variety of kidney diseases, both acute and chronic. The kidney biopsy procedure carries relatively low risk and yields substantial information. Potential complications include bleeding requiring transfusion, gross hematuria, arteriovenous fistula formation, and perinephric hematoma, among others. Percutaneous kidney biopsies are typically performed using real-time ultrasound or computed tomographic imaging. This Core Curriculum briefly outlines the history of the kidney biopsy, then discusses indications, complications, and specific procedural aspects.