Leprosy is believed to be transmitted only through human contacts. However, many anomalous observations had gradually accumulated which had weakened such beliefs. These are: only 1/3 rd cases of leprosy give a definite history of being transmitted from other known cases; life-long spouses, in whom only one has leprosy, seldom lead to leprosy to others; while MDT applied intensively in most leprosy endemic countries, could successfully reduce incidence of leprosy, however, simultaneously new cases arise unabated. Besides, a close look at animal leprosies also suggested a mode of transmission other than human-type contact. Thus, a search for alternative hypothesis led to the findings that leprosy bacillus (LB) could be a soil chemoautotroph and could facultatively live both in the human body and the soil which could serve as an alternative source of infection. Evaluation of accumulated evidences points to this possibility.