Formal mentorships should help new and aspiring administrators, yet there is little evidence about what works and what does not work in such programs. The study summarized in this paper explores demographic, relational, and operational characteristics of mentor dyads in both formal programs and informal pairings of aspiring and practicing administrators with more experienced administrators. Using multiple data collection methods (data comparisons, demographics analysis, and structured interviews), two populations were studied--40 pairs of practicing and prospective administrators participating in a statewide formal mentorship program and a stratified random sample of administrators pursuing naturally evolving mentoring relationships. Characteristics of formal and informal mentorships were found to be similar to mentorships in other occupations, though relational characteristics were the controlling factors in establishing a successful mentorship dyad. Traits of trust, mutual respect, openness, commitment, and friendship were reported as the most critical relational factors. Most dyads in both populations stressed professional aspects of their relationship over personal aspects. Where choice of partner existed, formal mentorships were rated as more successful than formal arrangements without choice. Informal mentorships, built on choice from the beginning, were rated more highly than the formal mentorships. Clearly, formal mentorships can benefit both mentors and proteges. Six aspects of successful formal programs are recommended. Six tables present survey data. (11 references) (MLH)