The linear instabilities of a geostrophically balanced frontal jet are computed numerically in an effort to understand the origin of intense small-scale cold-core features observed in the North Atlantic subtropical convergence zones during the Frontal Air-Sea Interaction Experiment (FASINEX). A simple analytic continuously-stratified basic state is used to represent the observed frontal structure. The most unstable linear modes have e-folding timescales of 2--3 days, along front wavelengths near 70 km, and significant asymmetry across the front. The results provide indirect evidence that baroclinic instability of the frontal jet is a possible source of the cold-core features observed during FASINEX. ¿ American Geophysical Union 1993