Lysosomal storage diseases (LSD) comprise a group of more than 40 different disorders, most of them resulting from a specific enzyme deficiency. The diagnosis of these disorders is often complicated due to their clinical and biochemical heterogeneity. Definitive diagnosis as well as prenatal diagnosis of LSD is based on specific enzyme assays. Analysis of urinary metabolites facilitates differential diagnosis of LSD, pointing to the probable enzyme defect. A flowchart for biochemical diagnosis is described. The goal of our work was to detect rapidly and reliably most of the known LSD.The results obtained in an 8-year period using this combined clinical/biochemical approach for 528 patients suspected of having LSD are presented. The diagnoses of 36 patients with different enzyme deficiencies show unambiguously the usefulness of the diagnostic algorithm.

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