Following the first reports of a prophylactic lithium action in recurrent affective disorders (Hartigan, 1963; Schou, 1963; Baastrup, 1964; Schou and Baastrup, 1966; Baastrup and Schou, 1967), a large number of research projects on this subject have been started. Prophylactic studies yield results slowly, and reports published to date are mainly of a preliminary nature. Some have been negative; the authors found little or no evidence of prophylactic lithium action (Fieve et al., 1968; Zall et al., 1968). Other observations seem to confirm the ability of lithium to prevent manic and depressive relapses (Achté et al., 1968; Blinder, 1968; Christodoulou, 1968; Dyson and Mendels, 1968; Gershon, 1968; Gottfries, 1968; Haastrup et al., 1968; Hofmann and Boleloucky-Bolen, 1968; Hullin et al., 1968; Kerry and Owen, 1968; Lauter, 1969; Levy, 1968; Melia, 1968; Sargant, 1968; Vaadal and Robak, 1968; Annell, 1969; Forssman and Wålinder, 1969; Fries, 1969; Uddenberg, 1969). The reports are based on samples which range from a few patients to about seventy. Few deal with systematic studies.