In this paper, indirect and direct integrity methods are compared in a challenge experiment with Bacillus subtillis spores used as a surrogate to Cryptosporidium oocysts. The challenge study was conducted with a cassette of 3 ZeeWeed(R) 500 ultrafiltration modules. Results for the intact membrane demonstrated a log removal value (LRV) larger than 7.0 based on feed concentration. The LRV was reduced to 5.2 with a pinhole and further to less than 4.0 with the two cut fibers. Turbidity did not allow the detection of the pinhole or cut fibers. The permeate particle counters did show significant departures from baseline when the membranes were compromised. Results are compared to LRVs estimated from a draft ASTM method. Includes 3 references, tables, figures, appendix.