Analysis of 22,510 urinary calculi between January 1991 to July 2000 performed by infrared spectroscopy allows for separation of drug-induced urolithiasis into two categories: first, the drugs physically embedded in the stone (n = 238; 1.0 per cent), notably indinavir monohydrate (n = 126; 52.9 per cent), followed by triamterene (n = 43; 18.1 per cent), sulphonamides (n = 29; 12.2 per cent) and amorphous silica (n = 24; 10.1 per cent); second, the category of metabolic nephrolithiasis induced by drugs (n = 140; 0.6 per cent), involving mainly calcium and vitamin D supplementation (n = 56; 40.0 per cent) and carbonic anhydrase inhibitors (n = 33; 23.6 per cent). Composition of the stone depended not only on the inducer drug but also on the metabolic state of the patient. Today, drug-induced stones comprise about 1.6 per cent of all calculi in France. Physical analysis and therapeutic history recall of such patients are the keys to diagnosis. Medical care is based on drug avoidance or dose adjustment with increased diuresis and, if necessary, change in urinary pH.