Maxillary transverse constriction is among the most common malformations in orthodontics. Treatment usually requires rapid palatal expansion with banded or bonded expanders after eruption of the maxillary first molars. The history of palatal expansion goes back nearly 150 years and has retained its popularity ever since. However, patient/guardian compliance in activating the screw with a key is required. Because it is difficult to see the hole on the screw, it is hard to insert the key through the hole. Furthermore, the chance of injuring the palatal mucosa with the pointed wire key and the risk of swallowing or aspirating the key are common undesired outcomes, and both occur in daily orthodontic practice. To overcome these unwanted incidences and make palatal exapanders more patient-friendly, a new design of palatal expander has to be developed for a safe, rapid, and effective expansion with minimum patient cooperation. A newly developed keyless expander has a built-in activation arm, which patients can activate themselves. In all 4 treated cases with a keyless expander, expansion was effectively achieved in a short period of time. World J Orthod 2008;9:407–411.