In the past, much effort has been devoted to determine stellar magnetic fields by means of the analysis of two spectral lines with different magnetic sensitivities (see, e.g., Robinson, 1980; Saar, 1988; Basri and Marcy, 1988). However, these methods are largely influenced by the uncertainties caused by, for instance, the presence of blends, uncertainties of atomic parameters, etc. Gray (1984) and, more recently, Basri et al. (1992) used a multiline analysis to measure stellar magnetic fields, reducing the importance of those uncertainties, thus increasing, in a statistical sense, the confidence of the results.

Here we present a new method based on the analysis of the equivalent widths of many Fe I spectral lines. The central idea is to obtain information on the magnetic field from the magnetic strengthening of the equivalent width of spectral lines. This technique has been applied to a weak-emission-line T Tauri star (TAP35) and a main sequence star (ξ Boo A), using data published by Basri et al., (1992).