Callus induction and plantlet regeneration from young leaves of high-yielding mature oil palm were carried out using 10-year and 20-year-old trees from Thepa Research Station, Faculty of Natural Resources,Prince of Songkla University, Hat Yai, and Trang Agricultural College, respectively. Culture media used in this experiment were Murashige and Skoog (1962) and Oil Palm supplemented with various concentrations of α-naphthaleneacetic acid (NAA) or 2,4- dichlorophenoxy acetic acid (2,4-D) or dicamba (Di) and antioxidants.Young leaves from 6th to 11st frond were excised, sterilized, cut into 5x5 mm pieces and cultured in the dark at 26±4ºC or 28±0.5ºC for 3 months. The results revealed that MS medium with 200 mg/l ascorbic acid (As) and 1 mg/l Di (MS-AsDi) gave the highest callus induction percentage (7.93) after culture for 3 months at 28±0.5ºC. Leaf segments from 6th - 8th frond yielded callus forming percentage at 10% (averaged from 1, 2.5 and 5 mg/l Di containing MS medium). Ascorbic acid as an antioxidant at concentration of 200 mg/l supplemented in MS medium in the presence of 2.5 mg/l Di produced the highest callus induction percentage (11.2) and number of nodules (7.06). A high percentage of embryogenic callus formation (66.67) was obtained when the calli were transferred to the same medium component supplemented with 0.5 mg/l Di and 1,000 mg/l casein hydrolysate (CH) (MS-AsDiCH). Haustorial-staged embryos were observed to be isolated as an individual embryo and germinated on MS medium without plant growth regulator (MS-free). Development of root could be classified into two distinct types, fibrous and tap root.