Most drilling problems result from unseen forces in the subsurface. But the equipment involved can also be a source of problems, as can personnel. The integrity of drilling equipment and its maintenance are major factors in minimizing drilling problems. Given equal conditions during drilling/completion operations, personnel are the key to the success or failure of those operations. Overall well costs as a result of any drilling/completion problem can be extremely high; continuing education and training for personnel directly or indirectly involved is essential to successful drilling/completion practices.