The cao-vit crested gibbon (Nomascus nasutus) is one of the world’s most endangered primate species, with one single protected forest patch supporting the last known population. In response to a report of a possible gibbon call having been heard in April 2009 about 5 km to the southwest of the protected gibbon habitat, we carried out a brief survey of the area in question. The habitat consisted of steep karst hills covered with secondary forest and shrubs, and valleys used for agriculture. However, some small strips of karst forest contained enough trees that they might support a gibbon group. During two days of field survey, no gibbons were seen, or heard calling, and the interview data we collected did not provide any recent evidence for the occurrence of gibbons in the area around Lung Ri. Although we found no evidence that gibbons occur in the Lung Ri area, the occurrence of gibbons there cannot be excluded due to the short duration of this study.