Spatial distribution and temporal variation of the interplanetary magnetic field (IMF) By-dependent cusp region field-aligned currents (FACs) during quiet periods were studied by use of magnetic data observed by Magsat. The analysis was made for 11 events (each event lasts more than one and a half days) when the IMF By component was steadily large and Bz was relatively small (‖Bz‖<‖By‖). Results of the analysis of total 62 half-day periods for the IMF By-dependent cusp region FAC are summarized as follows: (1) The IMF By-dependent cusp region FAC is located at around 86¿--87¿ invariant latitude local noon, which is more poleward than the location of the IMF Bz-dependent cusp region FAC. (2) The current density of this FAC is greater than previous studies (≥4 &mgr;A/m2 for IMF By=6 nT). (3) There are two time scales for the IMF By-dependent cusp region FAC to appear: the initial rise of the current is on a short time scale, ~10 min, and it is followed by a gradual increase on a time scale of several hours to a half day. (4) The seasonal change of this FAC is greater than that of the nightside region 1 or region 2 FACs. (5) The IMF Bz-dependent cusps region FAC is not well observed around the cusp when the IMF By-dependent cusp region FAC is intense. ¿ The American Geophysical Union 1989