Kaposi's sarcoma-associated herpesvirus (KSHV) establishes latent infections in lymphocytes and endothelial cells, and latent infection is closely linked to tumorigenesis. As few viral markers are expressed during latency, compounds that can safely and efficiently increase lytic gene expression in vivo have been sought. We have found that the non-tumour-promoting phorbol ester prostratin and the proteasome inhibitor bortezomib induce immediate-early, early and late KSHV gene expression from two lymphoma cell lines in vitro. Their ability to induce lytic gene expression supports a role for phorbol-ester and proteasome-regulated signalling pathways in KSHV reactivation and prompts further investigation of prostratin and bortezomib as therapeutic agents for KSHV-associated malignancies.