To evaluate the pharmacokinetics, safety, and tolerance of delavirdine mesylate ( U-90152 ) after multiple doses given orally to asymptomatic HIV-1 positive patients who are maintained on a stable dose of zidovudine ( AZT ). To investigate the optimum dose regimen of U-90152 that gives average trough concentrations > 1 micromolar in combination with standard AZT therapy, and to examine drug interactions between the two drugs. To establish the MTD of U-90152 in HIV-1 positive patients on stable AZT therapy. To investigate comparative pharmacokinetics between HIV-1 positive men and women.