We describe the clinical findings over the first 18 years of a patient with a novel phenotype for galactosialidosis, the storage disease produced by the combined deficiency of beta-galactosidase and neuraminidase. Clinical findings in the first few months included somewhat unusual appearance and hepatosplenomegaly. Dysostosis multiplex was evident by age 2 1/2 years. Mitral and aortic valvular disease appeared over the next few years and cardiac disease has become the most important clinical problem. Foam cells were present in the bone marrow, and vacuolated lymphocytes were present in the peripheral blood smear. The patient had no neurological symptoms, cherry red spots, or intellectual deterioration during the first 18 years. Evidence presented elsewhere indicates that the basic defect in this late infantile form of galactosialidosis (as is thought to be true for the other forms of galactosialidosis) is a reduced amount of the 32 kDa phosphoglycoprotein which associates with beta-galactosidase and alpha-neuraminidase in lysosomes.