Sabah is faced with a problem of small groups of orang-utans isolated from their parent populations in fragments of secondary forest, mainly on oil-palm plantations. The Wildlife Department has recently captured 84 such animals in three locations and translocated most of them to Tabin Wildlife Reserve, which already has a low-density population of orang-utans. The majority of animals were captured by drug immobilization, using a 5:1 ketamine/xylazine mixture at a mean dosage of 8.47 mg/kg body weight (range 3.76–22.64 mg/kg). This proved an effective and safe method. Others, mainly immatures, were captured manually. Few injuries or other problems were encountered. The cost of the rescue operations was $US175 per animal. A satisfactory way of monitoring the released orangutans is under development.