Although magnetic fields are presumed to be of substantial importance in the physics of stellar chromospheres (e.g., Vaiana et al. 1981), firm detections of magnetic fields in stars later than type A are rare, if not entirely absent. For example, Boesgaard (1974) made careful photographic measurements of longitudinal fields in a number of dwarf stars, and obtained 5 σ or greater detection of fields at the level of 100 G in the G8 V stars in ξ Boo A and in the KO V star 70 Oph A. Robinson et al. (1980) studied ξ Boo A by means of an analysis of the widths of magnetically sensitive lines, and obtained a mean field magnitude of 2600 G. However, Marcy (1981) used the same technique and found no significant field in this star. Brown and Landstreet (1981) looked for longitudinal fields in a variety of late type stars with an adaptation of a Griffin-type radial velocity spectrometer, which yielded standard errors near 10 G. They found no fields in any of the stars which they surveyed, including ξ Boo A, 70 Oph A, and a number of RS CVn stars and other stars with strong Ca II K and He I 10830 A emission.