A paleomagnetic record has been obtained from the middle Pleistocene sediments of the Humboldt River Canyon, Pershing County, Nevada. The age of the sediments is constrained by two tephra layers, the 610,000-year-old Lava Creek tephra and the approximately 495,000-year-old Dibekulewe tephra. The magnetization of the sediments is strong and stable, and the similarity of data from replicate sections strongly suggests that the data set represents an accurate record of the magnetic field except for the presence of postmagnetization rotations of less than 10¿. The influence of postmagnetization rotations was eliminated in one of the sections (HRlA) by rotating the paleomagnetic directions in accordance with the direction of the Lava Creek welded tuff previously determined from five sampling sites near Yellowstone National Park. After correcting the mean directions we observed nongeocentric axial dipole (non-GAD) mean directions of moderate amplitude (19¿¿13¿ in declination and 22¿¿8¿ in inclination) in the record from the HRlA section which may represent as much as 115,000 years of magnetic field behavior. In the youngest part of the Humboldt River Canyon sediments a zone of anomalous directions was recorded which we interpret to be a detailed record of an unconfirmed geomagnetic excursion. This record exhibits behavior consistent with that of previously reported polarity transitions. Because of the widespread nature of the tephras, especially the Lava Creek tephra, the prospects are very good for improving estimates of the magnitude and duration of the non-GAD paleomagnetic directions and, also, for confirming the excursion. ¿American Geophysical Union 1987