Long gone are the days when aviation maintenance technicians were able to maintain an aircraft with only on-the-job technical training. Today, we are faced with such complex and integrated aircraft systems that it is nearly impossible to maintain these aircraft without substantial technical training and reference resources. Lack of knowledge seems to be an ever growing problem in our industry as aircraft become more and more complex. In this sequence we will discuss some of the issues associated with lack of knowledge and what we as aviation maintenance professionals can do to avoid this all too common cause of human errors.