In February 1999, long-term hydroacoustic monitoring of the northern Mid-Atlantic Ridge (MAR) was initiated. Six autonomous hydrophones were moored between ~15¿N and ~35¿N on the flanks of the MAR. Results from the first year of data reveal that there is significant variability in along-axis event rate. Groups of neighboring segments behave similarly, producing an along-axis pattern with high and low levels of seismic activity at a wavelength of ~500 km. This broad scale pattern is likely influenced by the axial thermal regime. Several earthquake sequences with variable temporal characteristics were detected, suggesting fundamental differences in the cause of their seismicity. Off-axis, most seismic faulting occurs within a zone < 15 km from the axis center.