Mucopolysaccharidosis is a subset of lysosomal storage diseases. These diseases present a challenge to modern clinical and laboratory diagnostics due to the heterogeneity of symptoms and various forms of pathophysiological manifestation. Early diagnosis increases the chances of starting treatment and recovery, and this is only possible if there are fast and reliable tests. After setting the clinical suspicion, laboratory diagnosis of mucopolysaccharidosis begins with determining the concentration of glycosaminoglycans in the urine. The inspiration for this thesis was obtained from a study describing the results of a two-year FIND project in Spain. The Congenital Metabolic Diseases Diagnosis and Treatment Unit, in collaboration with the Spanish MPS Association for Rare Diseases, launched the FIND project to diagnose MPS early in children with symptoms and raise awareness of these diseases among pediatricians. Within this project, an in-house method was developed to determine GAG from dry spots of urine collected on filter paper. All procedures in this thesis are made according to the model and recommendation of the Laboratory for Metabolic Diseases of the Clinical Hospital Santiago de Compostela, Spain. The aim of the study was to examine the in house method for mucopolysaccharidosis screening in order to simplify the procedure of sending samples to the laboratory and speed up the diagnosis. The results obtained with in house method for samples from dry urine spots did not prove to be reliable, because GAGs are unevenly extracted from dry urine spots on filter paper. In addition, the method is more time consuming than expected. Therefore this in house method is not suitable for screening for mucopolysaccharidosis. Its possible application is possible only from liquid urine samples if no other method is available to the laboratory. Determination of GAGs by colorimetric method with Blyscan reagent is a reliable method for screening for mucopolysaccharidosis and is used in most metabolic laboratories.