- Abstract Giant arcs are found in the CLASH images and in simulated images that mimic the CLASH data, using an efficient automated arc-finding algorithm whose selection function has been carefully quantified. CLASH is a 524-orbit multicycle treasury program that targeted 25 massive clusters with 0.18< z< 0.90. Twenty of the CLASH clusters are selected based on their X-ray characteristics. The CLASH observations for each cluster consist of 16 broadband images (spanning the range 0.23 mu-1.6 mu) using the WFC3/UVIS, WFC3/IR, and ACS/WFC instruments on board HST. We run our arc finder on the detection (ACS+ WFC3/IR) image created for each cluster. We detect a raw total of 187 arcs with l/w>= 6.5 in 20 X-ray-selected CLASH clusters. After applying our minimum arc length criterion l>= 6", the arc count drops to 81 giant arcs selected from the 20 X-ray-selected CLASH clusters.