A PDU is a Professional Development Unit. Most often, it is equal to one contact hour. One AOTA CEU is equal to ten contact hours, or ten PDUs. For more clarification on the conversion from contact hours to PDUs when it is not an AOTA CEU course, please go to www.nbcot.org, click on "Certificants" in the left-hand menu, then on "Renewal Guidelines Handbook" in the left-hand menu. The handbook should give you all the information you need for NBCOT’s requirements and how to convert hours.