ordinary divinations. The shaman may be called on to engage in significant curing rituals. According to Hmong belief, spirits reside in the sky, and the shaman can climb a ladder to the heavens on his magical horse and contact the spirits there. Sometimes illness is caused by one's soul climbing the steps to the sky, and the shaman must climb after it, locate it, and bring it back to the body in order to effect a cure. During the ritual, the shaman sits in front of the altar astride a wooden bench, which becomes his or her horse. A black cloth headpiece covers vision of the present world, and as the shaman chants and enters a trance, he or she begins to shake and may stand on the bench or move, mimicking the process of climbing to heaven. The chant evokes the shaman's search and the negotiations with the heavenly spirits for a cure or for information about the family's fortune. Hmong shamans are believed to be chosen by the spirits, usually after a serious or prolonged illness. The illness would be diagnosed by another shaman as an initiatory illness and confrontation with death, which was caused by the spirits. Both men and women can be summoned in this way by the spirits to be shamans. After recovery from the illness, the newly chosen shaman begins a period of study with a master shaman, which may last two or three years, during which time he or she learns the chants, techniques, and procedures of shamanic rites, as well as the names and natures of all the spirits that can bring fortune or suffering to people. Because the tradition is passed orally, there is no uniform technique or ritual; rather, it varies within a general framework according to the practice of each master and apprentice. Christianity Christianity is a minority religion in Laos. There are three recognized churches in Laos: the Lao Evangelical Church, the Seventh-day Adventist Church and the Roman Catholic Church. There are approximately 45,000 members of the Roman Catholic Church, many of whom are ethnic Vietnamese, concentrated in major urban centers and surrounding areas along the Mekong River in the central and southern regions of the country. Catholicism is an established presence in five of the most populous central and southern provinces, and Catholics are able to worship openly. The church's activities are more circumscribed in the north.