Lysosomal storage diseases (LSDs) are a group of genetic disorders that result from defective lysosomal metabolism or export of naturally occurring compounds. Signs and symptoms are variable both within and between disorders depending on the location and extent of storage. Many patients develop neurologic symptoms that become obvious from the newborn period to adulthood. Diagnosis of suspected patients can usually be made by measuring the activity of an enzyme or concentration of a metabolite in easily obtained tissue samples. Based on the considerable diagnostic experience of our laboratory, we aid the physician in selecting the appropriate tests to perform. Hematopoietic stem cell transplantation and enzyme replacement therapy are already available or in clinical trials for a number of LSDs. Early diagnosis is critical, especially since those patients who are treated before significant symptoms arise have the best chance for a positive outcome.