I am not aware of research on the success rate of internal v.s. external consultants in change efforts. I would be very interested in any data you could share. In my opinion, self-dianosis (internal consultant method) works only if the organization is open to self-analysis and critisism. It requires a certain maturity and a culture that supports and is good at self-critique. Not many companies are in that position. There are also many political pitfalls for internnal consultants. However, if they are well trained in O.D. theory and intervention strategy and the culture supports it, internal consultants can be as effective as external consultants. Best wishes with your work! If you would like to discuss this further, my e-mail is hornfam@eosinc.com