We present a new approach to investigate the temporal fluctuations of seismicity in terms of intermittency as the underlying dynamical mechanism for the variability of seismic activity. Analyzing the 1983--1997 Irpinia (southern Italy) seismicity, we base our analysis on the multifractal formalism combined with the estimate of the correlation codimension. Our findings show that the seismic activity of the area investigated is strongly intermittent, and the degree of intermittency lowers if aftershock clusters, associated to the larger events, are removed. ¿ 2001 American Geophysical Union