Extremely low frequency (10--1500 Hz) magnetospheric chorus has been analyzed to investigate a possible dependence on substorms. Care was taken to separate effects from temporal effects by analyzing an entire year of data acquired by the Ogo 5 search coil magnetometer. A major finding of the study of spatial dependences is that chorus occurs principally in two magnetic latitude regions. Equatorial chorus is detected near the equator, and high-latitude chorus is found at magnetic latitudes above 15¿. When chorus in these two regions is analyzed separately, substorm dependences become apparent. Comparisons with AE indicate that equatorial chorus occurs primarily during substorms. High-latitude chorus is not strongly dependent on AE and often occurs during intervals of prolonged quiet with AE6 and strong diffusion for L>8. Instantaneous diffusion rates may be considerably higher owing to the discrete burstlike nature of the chorus. The spatial and temporal dependences of high-latitude chorus are considerably different from those of equatorial chorus. High-latitude chorus occurs in local day and evening and at large L. The emission is detected primarily on the dayside, at 0800?LT?1600, and often within 1--2RE of the magnetopause. The occurrence of high-latitude chorus during quiet intervals is consistent with local generation within 'minimum B pockets.'