The notion that nuclear factor-kappaB (NF-kappaB) is a tumor-promoting transcription factor has become a widely accepted dogma in biology. However, recent findings suggest an inhibitory role for NF-kappaB in carcinogenesis and tumorigenesis. Although the tumor suppressor-like effect of NF-kappaB remains to be rigorously established by further studies using cellular and animal models, these latest findings warrant caution with respect to blockage of NF-kappaB activation as a broad strategy in treating cancers.