Hydrographic and current observatons of the Norwegian Current (Horn and Schott, 1976) show a considerable amount of low-frequency variability; in particular, many of the current spectra are broadly peaked at around 2--3 days. In this paper wer consider a number of simple barotropic and baroclinic instability models of the mean flow in an attempt to explain these fluctuations. The theoretical results suggest that the current fluctuations are most likely due to baroclinic instability of the mean flow.