Drug prescribing for patients with renal failure should incorporate adjustment of dosage regimens in order to avoid accumulation and thus adverse effects. Drugs usually eliminated by the kidneys require the most modification. Since immediate therapeutic efficacy is of importance, the initial or loading dose is essentially unaltered for patients with renal dysfunction. Maintenance doses can be adjusted by either lengthening the interval between doses of by reducing the size of individual doses. In clinical practice, a combination of both methods is used. Serum levels should be used as guides whenever possible. In interpreting these levels, recognition of decreased plasma protein binding and prolonged elimination half-lives in renal failure is imperative. In patients requiring dialysis, consideration must be given to adjustments for drug removal by the artificial membrane. Small molecules unbound to proteins are most easily removed. Specific guidelines for therapy with common drugs prescribed for patients with renal failure are given. These include: (1) narcotics and analgesics; (2) psychotherapeutic drugs; (3) cardiovascular drugs; and (4) antimicrobial agents.