Cloud　computing　provides　the　essential　infrastructure　for　multi-tier　Ambient　Assisted　Living　(AAL)　applications　that　facilitate　people＇s　lives.　Resource　provisioning　is　a　critically　important　problem　for　AAL　applications　in　cloud　data　centers　(CDCs).　This　paper　focuses　on　modeling　and　analysis　of　multi-tier　AAL　applications,　and　aims　to　optimize　resource　provisioning　while　meeting　requests＇　response　time　constraint.　This　paper　models　a　multi-tier　AAL　application　as　a　hybrid　multi-tier　queueing　model　consisting　of　an　M/M/c　queueing　model　and　multiple　M/M/1　queueing　models.　Then,　virtual　machine　(VM)　allocation　is　formulated　as　a　constrained　optimization　problem　in　a　CDC,　and　is　further　solved　with　the　proposed　heuristic　VM　allocation　algorithm　(HVMA).　The　results　demonstrate　that　the　proposed　model　and　algorithm　can　effectively　achieve　dynamic　resource　provisioning　while　meeting　the　performance　constraint.