During a 2-week period, 3 hanuman langurs (Presbytis entellus) died from severe fibrinopurulent and proliferative peritonitis. Partially digested plant material was identified in the necrotic abdominal debris of the 1st and 2nd langurs. In the 3rd, a phytobezoar that extended 17.5 cm distally from the pyloric area had caused a 1-cm perforation. Seven months later, surgery was performed on a douc langur (Pygathrix nemaeus) to remove 1 gastric and 2 intestinal phytobezoars composed primarily of undigested Acacia sp leaves. An analysis of Acacia sp leaves consumed by these langurs revealed a high cell wall concentration (40%, dry basis), with an exceedingly high proportion of this cell wall composed of indigestible lignin. It was concluded that the species of acacia (Acacia saligna and A longifolia) fed in these cases are inappropriate browse items for langurs.