In many instances renal papillary necrosis (RPN) can be diagnosed with confidence on the basis of typical x-ray patterns. Three cases of RPN following phenacetin abuse are reported from private practice, indicating that phenacetin addiction with resultant renal damage may not be rare in the United States. Establishing the presence of RPN has become important clinically because of the following reasons: (1) Renal destruction in phenacetin habitués can be arrested by discontinuing the drug. (2) Recognition of RPN in diabetic patients makes possible vigorous, lengthy antimicrobial therapy resulting in prolonged and useful lives. (3) In a few acute, unilateral cases nephrectomy may be life-saving. (4) Ability to recognize the disease on x-rays allows search for other drugs that could cause the necrosis. The authors have found that the medullary form of renal necrosis occurs in sickle-cell disease.