Informal mentoring is based on a natural match between a junior individual and a senior one who share mutual interests. It usually aids in the professional and personal development of both parties involved. We reviewed the literature regarding factors that make informal mentoring effective within the medical realm, by searching a major academic search engine, Web of Knowledge, for the term "informal mentor". Our main research questions concerned the factors that lead to a successful informal mentorship process. A salient finding arising is that the success of informal mentorships hinges on the communication skills of mentor and protégé, their level of commitment, and the chemistry between the partakers. Good informal mentorships impose requirements on both mentors and protégés and rest on shared expectations.