Forty patients currently taking zidovudine (AZT) or any other approved antiretroviral agent will be randomized to one of three treatment arms: high-dose nimodipine, low-dose nimodipine, or placebo. Additionally, six patients who are intolerant to standard antiretroviral therapy will be randomized to receive high- or low-dose nimodipine. Nimodipine is administered by mouth concurrently with patients' prestudy dose of antiretroviral agent. Treatment is given for 16 weeks, and patients are followed every 4 weeks. As an option, all patients may receive an additional 16 weeks of low-dose nimodipine.