Six asymptomatic HIV-infected males, or those with limited symptoms of early AIDS-related complex ( ARC ), will receive one dose intravenously of ranitidine in distilled water and one dose of placebo (distilled water alone), followed in 1 hour by foscarnet in oral solution. The order of ranitidine and placebo is randomized and the two foscarnet doses are separated by at least 72 hours. A nasogastric pH probe is placed on each morning of drug administration to monitor gastric pH.