Oldenlandia diffusa (OD) and Scutellaria barbata (SB) have been used in traditional Chinese medicine for treating liver, lung and rectal tumors. In this study we determined the effects of these phytochemicals on oxidative burst as an indicator of phagocytic function in a murine macrophage cell line J774 using an automated micro-fluorometric assay. A dose-dependent augmentation of oxidative burst was observed with OD as well as SB. The effect of OD and SB on the growth of a murine renal cell carcinoma (Renca) was also determined. Balb/c mice were transplanted subcutaneously with 1 x 10(5) Renca cells and were randomized into groups of 10 to receive oral feeding of OD (4 mg/day), SB (4 mg/day), or saline as control. Oral feeding with either OD or SB significantly inhibited the growth of Renca in mice. The data of this study show that OD and SB are capable of enhancing macrophage function in vitro and inhibiting tumor growth in vivo.