||This study is a social psychological investigation of the mental health of proselyting missionaries, specificalIy Mormon missionaries, and their social context. The study consists of two parts: (a) a general historical and cultural background of the Mormon missionary system--its origin and development; and (b) the contemporary missionary system with its supports and strains as related to the mental health of missionaries" The theoretical framework for the study is based on socialization and its relation to mental health. More specifically, the study focused on three phases of the socialization process involved when an individual moves into a new social role: (I) pre-entry period--preparation and anticipatory socialization; (2) role participation; and (3) exit from role. A major assumption was that socialization may contribute to mental healthiness or mental unhealthiness of the individuals involved" *" "Mormon" refers to members of the Church of Jesus Christ of Latter-day Saints. The data for part "a" of the study were based on books and other documents of Mormon history and interviews with Mormon scholars" The data for part "b" were based on recent Mormon literature and personal interviews with a random sample of members and pledges of Delta Phi Kappa, a fraternity for returned missionaries Ideal types were constructed for (a) supports and strains--both structural and international --and (b) effects--mentally healthy and mentally unhealthy. The findings related to the ideal types were represented by frequencies and percentages and by modal patterns and rank orders. Mental healthiness was defined as including: (I) self-acceptance; (2) healthy personal identity; (3) personal satisfaction with level of functioning; (4) valuing of accomplishment in terms of its intrinsic or self-enhancing satisfaction; (5) social adjustment; (6) agility to give and receive love; (7) relating in characteristic ways to other individuals in the environment; (8) ability to seek strength and to share one's strength with appropriate others; (9) clinical adjustment; (10) flexibility when under stress; and (I I) being in good spirits most of the time. Mental unhealthiness was defined as: (l) disturbances in thinking; (2) mood disorders; (3) disorders of behaviors; (4) marked anxiety; (5) prolonged sleep disturbance; (6) pathological use of sex; and (7) psychophysiology reactions. Findings Part A. The Mormon missionary system which began In 1830 has become a vast system of proselyting In many countries of the world. As the system has developed, changes have been made from time to time. For example, early missionaries traveled without purse or scrip. Today, Mormon missionaries travel at their own expense (or that of their families) and they proselyte using standardized techniques including lesson plans which they have memorized. Part B, The contemporary Mormon missionary system includes proselyting throughout the non-communist world. Most of the missionaries are young men between the ages of 19 and 25 who interrupt their education or employment to serve two-year missions for their church. Supports and strains exist during the pre-entry period, during the time in the mission field, and up the missionary's return home. This study revealed that during the pre-entry period the most important factor for mental healthiness was the missionary's family. Other factors related to mental healthiness included friends, the bishop and stake president, and other missionaries in the mission home. Important factors for mental unhealthiness during the pre-entry period were the content and schedule of activities in the mission home and leaving one's girl friend and family. During the period in the mission field the significant factors for mental healthiness of the missionaries were the mission president, success, first companion, and Mormons in the mission area. The most important factors related to mental unhealthiness were companions (excluding one's first companion), leaving the mission field, and cultural shock. For the return home period the most important factor for mental healthiness was the family of the returned missionary. Other factors related to mental healthiness included education, Delta Phi Kappa fraternity, and friends. The most significant factor for mental unhealthiness was dating. Another factor, though seemingly less important than dating, was not being busy. When the total effects of the overall mission experience were judged the ratio of healthy effects to unhealthy effects was 1.42 to one. Several recommendations were made for increasing the mental healthiness of proselyting missionaries and for further research.