The Collaborative International Dictionary of English v.0.48:

hospitalisation \hospitalisation\, hospitalization
\hospitalization\n.
   medical care in a hospital; also, the period during which one
   receives care in a hospital.

   Syn: hospital care.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

hospitalisation
    n 1: placing in medical care in a hospital [syn:
         hospitalization, hospitalisation, hospital care]