The use of vitamin A therapy during human immunodeficiency virus (HIV) infection is under clinical investigation, and vitamin A could potentially modulate HIV replication because the virus genome contains a retinoic acid response element. A randomized, double-masked, placebo-controlled clinical trial was conducted to determine the impact of single high-dose vitamin A supplementation, 60-mg retinol equivalent (200,000 IU), on HIV load and CD4 lymphocyte count. HIV-infected injection drug users (120) were randomly allocated to receive vitamin A or placebo. Plasma vitamin A level, CD4 lymphocyte count, and HIV load were measured at baseline and 2 and 4 weeks after treatment. Vitamin A supplementation had no significant impact on HIV load or CD4 lymphocyte count at 2 and 4 weeks after treatment. This study suggests that high-dose vitamin A supplementation does not influence HIV load.