This chapter discusses nephrology. The term glomerulonephritis indicates an inflammatory process involving the glomeruli in the kidneys. It is important to specify that the process involves the glomeruli primarily to differentiate it from a similar process in the other compartments in the kidney, e.g. tubulointerstitial nephritis involving the interstitium, pyelonephritis involving the kidney parenchyma and the urinary tract, etc. Acute glomerulonephritis (AGN) is often called “postinfectious nephritis” making it clear what the pathogenetic process is. It is an inflammatory process that is triggered off in the kidneys following an infection. Urinanalysis usually shows plenty of red blood cells (RBCs) in association with RBC casts, leucocytes and proteinuria. The renal function and proteinuria, usually resolve in 1–2 weeks. Within 3–4 weeks, all antihypertensive medications can usually be stopped.