Six asymptomatic HIV-infected patients are treated with AZT orally every 8 hours on days 1 through 4, then with a single dose on day 5 (after 8 hours of fasting), followed by pharmacokinetic sampling. On days 6 through 9, patients receive AZT orally every 8 hours in combination with valproic acid (lowest dose in the first 5 patients and a higher dose in patients 6 and 7) orally every 8 hours. On day 10, AZT and 1 of the 2 doses of valproic acid are given orally as single doses, followed by pharmacokinetic sampling. AZT is continued alone orally every 8 hours on days 11 through 14, then resumed at the patient's usual dose beginning on day 15. Per 03/09/92 amendment, dosing schedule may be modified slightly to accommodate patients with scheduling conflicts.