Recent reports suggest that green tea consumption may prevent or delay the growth of human cancer, possibly by impairing tumor invasion and/or by an anti-angiogenic effect. In NOD/SCID mice transplanted intraperitoneally with human non-Hodgkin's lymphoma (NHL) cell lines, Namalwa, RAP1-EIO and HS-Sultan, green tea prevented 50% of Namalwa tumors (P = 0.0017 by log-rank) and significantly inhibited RAP1-EIO and HS-Sultan tumor growth. Notably, treatment with the chemotherapy drug cyclophosphamide at the maximum tolerable dose was unable to prevent Namalwa tumor occurrence. In the three models evaluated, the frequency of apoptotic endothelial and tumor cells was significantly increased in mice given green tea compared to controls. These results support further trials in NHL to evaluate whether green tea, alone or in combination with chemotherapy, may delay or prevent disease progression.