Fragmentation in sublevel caving (SLC) is vitally important. Both gravity flow and any downstreamprocesses are affected. Fairly coarse fragmentation may lead to larger draw bodies (isolatedextraction zones) and hence potentially higher primary ore recovery and depressed/delayedwaste rock inflow from above. Fewer flow disturbances are expected by mitigating oversize. Inaddition, it requires less boulder handling and reduces wear and possible hang-up problems inorepasses. To assess the present-day functionality of large-scale SLC, a multiyear, comprehensivemeasurement program was initiated. It covers the main elements for SLC, namely blast function,fragmentation and gravity flow. The present paper focuses on fragmentation measurements. Animage acquisition system was used to document the drawpoint and the load-haul-dump (LHD)bucket for each mucking cycle. At the beginning, four buckets (about 70 t total) were sieved tovalidate the results of both 2D and 3D image analysis techniques. The fundamental and specificproblems are discussed herein. At the moment, fragmentation of the SLC rings is evaluated usinga quick rating system and a 2D fragment delineation software. The results enable a descriptionof fragmentation and its variation during mucking but also – combined with the gravity flowmeasurements – conclusions on the fragmentation for different parts of the SLC ring. Possibleinfluences on flow disturbances and ore recovery/dilution are investigated. The recent findingsallow a better understanding of breakage and flow and support future process improvements.