Protein kinase C (PKC) appears to play a role in replication of human immunodeficiency virus type 1 (HIV-1). PKC is a family of at least 12 isozymes. In this study, we investigated a role of Ca²⁺-dependent PKC isozymes (α, β, and γ) in activation of latent HIV-1 in U1, a chronically infected promonocytic cell line, using polyclonal rabbit anti-PKC isozyme antibodies as specific inhibitors. Antibodies were introduced intracellularly by electroporation and then cells were stimulated with PMA. HIV-1 production was measured as p24 antigen using ELISA and reverse transcriptase activity. Anti-PKCβ antibody significantly inhibited PMA-induced HIV-1 production, whereas antibodies against PKCα and γ had no significant effect. Furthermore, anti-PKCβ antibody inhibited PMA-induced activation of NF-kB and HIV-1 LTR. Preincubation of anti-PKCβ antibody with its antigenic peptide reversed the inhibitory effect of anti-PKCβ antibody. This study suggests that PKCβ plays a role in PMA-induced activation of latent HIV-1.