To evaluate whether socioeconomic status is associated with risk of malpractice claims, particularly among those who have suffered medical injury. Case-control study. Fifty-one hospitals in New York State. The presence and severity of medical injury, defined as disability at the time of discharge or prolongation of the hospitalization caused by medical treatment as opposed to the disease process, were assessed through review of approximately 31,000 hospital records in New York in 1984. These sampled records were then linked to formal malpractice claims. To estimate the risk of malpractice claims by age, gender, race, insurance status, and income, we conducted a case-control study of claimant cases matched with nonclaimant controls. The cases were all those patients who filed malpractice claims referring to alleged malpractice during a sampled hospitalization. Physician reviewers had previously judged the level of disability that resulted from the medical injury. Claimants (n = 51) were each matched with five nonclaimant controls on the basis of injury. Noninjured cases were matched with noninjured controls and injured cases were matched with injured controls. We found that poor patients (odds ratio [OR], 0.2; 95% confidence interval [CI], 0.03 to 0.8) and uninsured patients (OR, 0.1; 95% CI, 0.005 to 0.9) were significantly less likely to file malpractice claims, after controlling for the severity of medical injury. Among patients who suffered medical injury, the elderly (OR, 0.2; 95% CI, 0.03 to 0.9) were also less likely to file claims. Gender and race were not independently associated with risk of malpractice claims. Poor and uninsured patients are significantly less likely to sue for malpractice, even after controlling for the presence of medical injury. Fear of malpractice risk should not be a significant factor in the decision to serve the poor. Tort reforms that would protect physicians who serve the medically indigent from malpractice suits may not be warranted.