Summary 1) Further examples of quantity and types of urinary excretion of sulfated mucopolysaccharides in Hurler's syndrome have been studied in 9 cases. All excreted both ChS-B as the major component and heparitin sulfate as a minor constituent. 2) In one case, excretion of mucopolysaccharides dropped after prednisone administration. 3) From various organs of 5 autopsy cases, the 2 polysaccharides were isolated. 4) Livers of 4 cases contained between 1.2 and 6.7% of total mucopolysaccharides (on fat-free dry wt). In 3 of these, 90% was heparitin sulfate, but from all of these, also some ChS-B was obtained. One liver had approximately equal quantities of the 2 polysaccharides. 5) In one case, spleen, brain and kidney of the same individual also yielded both polysaccharides, but in proportions remarkably different from those of liver. Brain of 2 additional cases also yielded the 2 mucopolysaccharides. One of these contained 85% of ChS-B. The brain of a normal child did not yield any chondroitin sulfate, but hyaluronate and heparitin sulfate.