The present invention relates to tricyclic inhibitors of beta-secretase having the structure shown in Formula (I) and (II)and the tautomers and the stereoisomeric forms thereof, wherein the radicals are as defined in the specification. The invention is also directed to pharmaceutical compositions comprising such compounds, to processes for preparing such compounds and compositions, and to the use of such compounds and compositions for the prevention and treatment of disorders in which beta-secretase is involved, such as Alzheimer' s disease (AD), mild cognitive impairment, senility, dementia, dementia with Lewy bodies, Down' s syndrome, dementia associated with stroke, dementia associated with Parkinson' s disease, dementia associated with beta-amyloid, age-related macular degeneration, type 2 diabetes and other metabolic disorders.