Multi-temporal　airborne　laser　scanning　(ALS)　surveys　have　become　a　prime　consideration　for　detecting　landslide　movements　and　evaluating　landslide　risk　in　mountain　areas.　The　minimum　elevation　change　(or　detectability)　that　can　be　detected　by　repeated　ALS　surveys　has　become　a　critical　threshold　for　landslide　researchers　and　engineers　to　decide　if　ALS　is　a　capable　tool　for　detecting　targeted　landslides　and　arranging　the　minimum　time　span　between　two　scans　if　ALS　is　a　choice.　The　National　Center　for　Airborne　Laser　Mapping　(NCALM)　at　the　University　of　Houston　conducted　three　repeated　ALS　surveys　at　the　Slumgullion　landslide　site　in　Colorado,　U.S.　over　one　week　in　July　of　2015.　These　repeated　ALS　surveys　provide　valuable　datasets　for　evaluating　the　vertical　detectability　of　multi-temporal　ALS　surveys　in　a　typical　mountain　area.　According　to　this　study,　the　difference　of　digital　elevation　models　(DDEM)　derived　from　ALS　has　the　ability　of　detecting　a　minimum　elevation　change　of　5　cm　over　flatter　and　moderately　rugged　terrain　areas　(slope　＜　20　degrees)　and　a　minimum　of　a　10-cm　elevation　change　over　rugged　terrain　areas　(20　degrees　＜　slope　＜　40　degrees).　However,　the　DDEM　values　over　highly　rugged　terrain　areas　(slope　＞　40　degrees),　such　as　cliff　and　landslide　scarps,　should　be　interpolated　with　caution.　Global　Navigation　Satellite　Systems　(GNSS)　and　Terrestrial　Laser　Scanning　(TLS)　surveys　were　also　performed　at　the　middle　portion　of　the　landslide　area　for　assessing　the　accuracy　of　ALS　datasets.　The　accuracy　of　ALS　varies　from　approximately　one　decimeter　(~10　cm)　to　one　foot　(~30　cm)　depending　on　the　roughness　of　terrain　surface　and　vegetation　coverage　(point　density).　The　detectability　and　accuracy　estimates　of　ALS　measurements　obtained　from　the　case　study　could　be　used　as　a　reference　for　estimating　the　performance　of　modern　ALS　in　mountain　areas　with　similar　topography　and　vegetation　coverage.　©　2018　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.