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The objective of this paper is to present a brief overview of effects of condensed tannins (CT) on ruminant nutrition and animal production. Tannins are phenolic secondary compounds and are widely distributed in the plant kingdom. CT are the most common type of tannin found in temperate legumes, trees, and shrubs. Tannins exist primarily as CT and hydrolyzable tannins (HT). HT are potentially toxic to ruminants. Pyrogallol, a hepatotoxin and nephrotoxin, is a product of HT degradation by ruminal microbes. However, CT are considered to be non (or less)-toxic because they are not absorbed from the intestine. CT often precipitate with dietary proteins at pH 5.5 to 7.0, with the extent of this reaction being dependent on the concentration, molecular weight, and structures of the CT and of the protein. Low concentrations of CT (2 to 4% CT, DM basis) in several temperate plant species (e.g., Lotus corniculatus, sulla, and sainfoin) are beneficial for ruminants, and have resulted in improved milk yield, wool growth, live weight gain, ovulation, and lambing percentage, as well as preventing pasture bloat and reducing internal parasite burden. This is related to the reduced protein solubility and degradation in the rumen and to enhanced flow of non-ammonia nitrogen to the abomasum and to increase absorption of essential amino acids from the small intestine. However, high forage CT concentrations (5 to 10% CT) reduce voluntary feed intake and digestibilities, especially in tropical regions where feed choices and quality are limited. At present, there are a few opportunities for reducing the negative effects of high CT concentrations in these regions and future progress for improving ruminant productivity is dependent on improving our understanding of the chemical structure of CT from various plants and understanding how CT affect ruminal microbes and forage nutritive value. Key Words: Condensed tannins, Ruminant, Nutritive value