A controlled-source electromagnetic monitoring system located near the summit of Kilauea has been in operation since mid-1979. Prominent changes in the controlled-source magnetic fields have been observed both preceding and following two seismic swarms that are interpreted to be related to shallow magma intrusions in August 1980 and January 1981. The vertical magnetic field (Hz) sensor nearest the sites of intrusion showed the largest field changes. All comparisons to data have been made at 1 Hz, which corresponds to a depth of penetration of several kilometers. Large and rapid vertical-magnetic field changes were measured following the intrusion into the upper east rift of Kilauea on August 27, 1980. Similar fluctuations were measured both before and during the intrusion into the southern caldera on January 20, 1981. Located earthquakes and data from a recording tiltmeter within 2 km of the Hz sensor, which showed anomalous field changes over the January 20 event, indicate that the Hz sensor was located nearly over the zone of intrusion. The Hz field changes recorded over both the August 1980 and January 1981 intrusive events appear too large to have been caused by conductivity changes within a horizontally layered section. More probably, they were caused by relatively shallow intrusion of high-conductivity magma into open high-angle fracture or by establishing continuity of short sections of preexisting magma storage zones, thereby producing long linear conductors from short, normally discontinuous conductive segments.