Colobine monkeys differ from all other primates in having a foregut fermentation system featuring a complex, multi-chambered stomach with either three or four chambers where a commensal microbiome digests plant cell walls and possibly detoxifies defensive plant chemicals. Obtaining information on their morpho-physiological digestive traits, focusing on their forestomach physiology, is indispensable for understanding the mechanism underlying their ecology and behaviour. Additionally, such information would be useful for their zoological management as colobines have often been considered difficult to maintain healthy in captivity. There are new developments in our understanding of colobine digestive strategies, especially in terms of behavioural level, e.g., “rumination strategy” and resting posture, and physiological level, e.g., digesta flow and microbial patterns, though there has not been much progress in terms of clarifying their anatomical attributes since the previous 1994 review. In this chapter, we overview the recent findings on colobine digestive strategies, focusing on their forestomach.