The National Nursing Home Improvement Collaborative aimed to reduce pressure ulcer (PU) incidence and prevalence. Guided by subject matter and process experts, 29 quality improvement organizations and six multistate long-term care corporations recruited 52 nursing homes in 39 states to implement recommended practices using quality improvement methods. Facilities monitored monthly PU incidence and prevalence, healing, and adoption of key care processes. In residents at 35 regularly reporting facilities, the total number of new nosocomial Stage III to IV PUs declined 69%. The facility median incidence of Stage III to IV lesions declined from 0.3 per 100 occupied beds per month to 0.0 (P<.001) and the incidence of Stage II to IV lesions declined from 3.2 to 2.3 per 100 occupied beds per month (P=.03). Prevalence of Stage III to IV lesions trended down (from 1.3 to 1.1 residents affected per 100 occupied beds (P=.12). The incidence and prevalence of Stage II lesions and the healing time of Stage II to IV lesions remained unchanged. Improvement teams reported that Stage II lesions usually healed quickly and that new PUs corresponded with hospital transfer, admission, scars, obesity, and immobility and with noncompliant, younger, or newly declining residents. The publicly reported quality measure, prevalence of Stage I to IV lesions, did not improve. Participants documented disseminating methods and tools to more than 5,359 contacts in other facilities. Results suggest that facilities can reduce incidence of Stage III to IV lesions, that the incidence of Stage II lesions may not correlate with the incidence of Stage III to IV lesions, and that the publicly reported quality measure is insensitive to substantial improvement. The project demonstrated multiple opportunities in collaborative quality improvement, including improving the measurement of quality and identifying research priorities, as well as improving care.