Nephrolithiasis is a common disorder and a significant problem because of incidence, recurrence and severe consequences. Stone disease is a surgical as well as a medical problem. Major progress has been made recently in understanding the pathophysiological disturbances responsible for stone formation as well as in the techniques of stone removal. The introduction of extracorporeal shock wave lithotripsy has considerably reduced the need for surgery. Improvements in methods of kidney stone removal have not diminished the need for the application of an effective prophylactic program. The internist should take a complete history of stone events (number, composition, location and outcome of stone event), family history of stones, dietary habits (focusing on the consumption of animal protein, salt and dairy products), medications and physical examination. Radiopaque stones should be documented by plane X-ray films. Ultrasonography should be used to image calculi that are nonopaque, and to easily distinguish them from masses such as tumour or blood clot. Computed tomography is also an excellent method for imaging nonopaque renal calculi but higher cost and radiation exposure are disadvantages . Crystallographic analysis is the essential diagnostic procedure. If available, previous stones should also be examined. "In stone disease, everything is measurement. What the laboratory cannot tell you, you will not know; what it tells you in error, you will not correct by using your instincts, your medical experience, or your art ". Reliable diagnostic protocols are available for the identification of different causes of stones. The complexity of protocols depend on the severity of nephrolithiasis. Patients with a single stone episode undergo simple protocol, and extensive detailed protocol is used for patients with recurrent stone disease, or patients at increased risk. Simple protocol, besides the already mentioned history of stone events, radiographic investigation and crystallographic analysis, includes serum urea, creatinine, uric acid, sodium, calcium, phosphorus and protein levels, urinary pH and volume, urine samples for culture and urinary calcium, uric acid, oxalate and citrate. Extensive metabolic evaluation includes simple protocol, determination of serum levels of alkaline phosphatase, parathyroid hormone, thyroxin, magnesium. A 24-h collection of urine specimen is analysed for urea, creatinine, uric acid, calcium, phosphate, sodium, magnesium, oxalate and citrate. Extensive protocol includes specialized evaluation tests . Urinary acidification test is important for detecting distal renal tubular acidosis. Two 24-h urine specimens are collected while the patient is on the regular diet. The patient is then placed on a restricted diet (400 mg of calcium and 100 mEq of sodium) for a week, and another 24-h urine sample is collected. After that fasting and calcium load tests are performed (Sheme 1). Fasting urinary calcium is used to detect renal calcium leak, and calciuric response to oral calcium load provides an indirect measure of intestinal calcium absorption. Diagnostic criteria for major forms of stone disease  are presented in Table 1. There are some still unsolved questions: does time after passage of stones or urological intervention influence the frequency of urine abnormalities that can be detected; are there differences in 24-h urine composition between weekdays and weekends: what is the prevalence of the most important urinary risk factors of recurrent idiopathic calcium nephrolithiasis: do male patients differ from females with respect to urinary risk factors or recurrent idiopathic calcium nephrolithiasis? .