Background: Longitudinal studies of the glycoproteinoses have been undertaken to detail the natural course of these rare diseases, assess genotype–phenotype correlations, and establish clinical and laboratory databases. The Greenwood Genetic Center hosted Glycoproteinoses Clinics in July, 2012 in conjunction with the Third International Conference for Glycoproteinoses in Charleston, South Carolina. Methods: Every patient attending the multi-disciplinary clinic was evaluated by a geneticist, cardiologist, dentist, neurologist, ophthalmologist, orthopedist, and psychologist. All patients had electrocardiogram, transthoracic echocardiogram, and cognitive testing (KBITII or DAYC). Adaptive functioning measures (Vineland Adaptive Behavior Scale) and Parent Stress Index were completed for most patients. Blood, urine, and fibroblasts were collected from patients and parents. Diagnoses were confirmed with biochemical studies, and causative genes were sequenced. Results: Six different glycoproteinoses disorders were represented in this cohort of thirty patients, ages 2–40 years: alpha-mannosidosis (7), mucolipidosis (ML) II (2), ML III (17, including four patients best categorized as having intermediate ML II/III), fucosidosis (1), galactosialidosis (1), and aspartylglucosaminuria (2). Analysis of the extensive data collected is ongoing but has already yielded new insights for each condition. For example, findings in patients with alphamannosidosis include normocephaly 7/7, retinal vasculature tortuosity 6/7,mandibular torus or buccal exostosis 4/7, and tooth discoloration 5/ 7. For the first time, GNTPAB genotype/cardiac phenotype correlations are made. Novel mutations are reported for FUCA1, MAN2B1, AGA, and GNPTAB genes. Conclusions: Glycoproteinoses Clinics 2012 yielded extensive natural history data and rare laboratory samples. Clinical, biochemical, and molecular data will be presented.