Quality problems have long plagued the nursing home industry. While two-thirds of U.S. nursing homes are investor-owned, few studies have examined the impact of investor-ownership on the quality of care. The authors analyzed 1998 data from inspections of 13,693 nursing facilities representing virtually all U.S. nursing homes. They grouped deficiency citations issued by inspectors into three categories ("quality of care," "quality of life," and "other") and compared deficiency rates in investor-owned, nonprofit, and public nursing homes. A multivariate model was used to control for case mix, percentage of residents covered by Medicaid, whether the facility was hospital-based, whether it was a skilled nursing facility for Medicare only, chain ownership, and location by state. The study also assessed nurse staffing. The authors found that investor-owned nursing homes provide worse care and less nursing care than nonprofit or public homes. Investor-owned facilities averaged 5.89 deficiencies per home, 46.5 percent higher than nonprofit and 43.0 percent higher than public facilities, and also had more of each category of deficiency. In the multivariate analysis, investor-ownership predicted 0.679 additional deficiencies per home; chain-ownership predicted an additional 0.633 deficiencies per home. Nurse staffing ratios were markedly lower at investor-owned homes.