Alpha-Mannosidosis is a rare Lysosomal Storage Disorder with a worldwide incidence of about 1:500 000. This orphan and devastating disease is caused by the deficiency of the lysosomal alpha-mannosidase (LAMAN) which is responsible for the intralysosomal degradation of mannosyl linked oligosaccharides. To date no causative treatment for alpha-Mannosidosis is available and since most of the children are born healthy, an early initiated therapy could contribute to a normal development. To develop an efficient therapy for this disease the collaborative research project EURAMAN and HUE-MAN were initiated within FP5 and FP6, respectively. Within these collaborative networks, European scientists, clinicians and the industry successfully i) developed an efficient pre-clinical Enzyme Replacement Therapy (ERT) protocol using recombinant human (rh) LAMAN in a mouse model for alpha-Mannosidosis, ii) built up a database collecting patient data and iii) defined clinical endpoints for the future clinical trials in alpha-Mannosidosis patients by an European wide natural history study. Furthermore, the HUE-MAN network developed the conditions for a large-scale production of the recombinant enzyme and the way is now paved for the first clinical trials in man, which we aim to realize within FP7. The main objectives of the ALPHA-MAN project are i) the performance of efficient clinical trials (phase I-III) in alpha-Mannosidosis patients, ii) a better understanding of the pathophysiology and the mechanism of how the recombinant enzyme enters the cells of the central nervous system by performing ERT in a newly generated immuntolerant alpha-Mannosidosis mouse model, which allows chronic treatment and iii) the determination of the minimal effective dose with chronic treatment in the immuntolerant mice.