Persons accepted into the study will take AZT capsules every 4 hours (6 times daily) for 42 days. Treatment with AZT should start as soon as possible, but no later than 5 days, after exposure to the HIV. Blood and urine samples for various studies will be taken at intervals during the 42-day treatment period, and blood samples will be taken every 3 months for 1 year and every 6 months for 2 years and tested for signs of HIV infection (HIV antibody determinations).