AZT is the only antiviral agent that has been shown to be effective in patients with severe HIV infection. However, AZT is largely eliminated from the body through a biochemical reaction that takes place in the liver, and it is possible that patients with underlying liver disease may have altered AZT pharmacokinetics and may metabolize AZT differently, with the result that they are susceptible to an increased risk of serious drug toxicity. This study will examine the pharmacokinetics, elimination, and metabolism of AZT in patients with liver disease. Guidelines developed from the data will be helpful in managing AZT treatment of these HIV-infected persons and will indicate whether the dose of AZT administered should be adjusted to compensate for any changes in its bioavailability and/or pharmacokinetics.