Between 1967 and 1983, four earthquake swarms occurred on Kilauea Volcano, Hawaii, with durations ranging from 68 to 156 hours. Plots of the number of events per hour show a remarkable modulation having diurnal and semidiurnal periodicities. We test the hypothesis that these fluctuations are tidally triggered. A correlogram showing the correlation coefficient between the swarm series and tidal strain oriented at 20¿ intervals and phase shifted at 1-hour intervals gives the orientation and phase of the tidal strain most closely resembling the swarm plots. Maximum correlation occurs at different orientations and phases for three of the four swarms, which occur in tectonically different parts of the volcano. Two of the swarms which occur in the same region can be fit with a common tidal forcing function even though they occurred more than a year apart. The discrete Fourier transform of the swarm data shows a dominance of diurnal energy over semidiurnal energy, compared with the opposite dominance for the transform of the theoretical tidal function at the times of the swarms. We checked whether the diurnal dominance might be generated by culture noise by raising the threshold magnitude of the earthquakes used without noticeably affecting the results. Also the phase of the correlation varies from swarm to swarm relative to local Hawaii time. Diurnal dominance remains not completely understood, but tidal influences appear to be the best explanation for the modulation of the activity. These observations limit the rate of tectonic stress change in the rift zones of Kilauea to less than the tidal stress rate. ¿ American Geophysical Union 1988