A search of Mariner 10 electron plasma and magnetic field measurements has revealed 14 examples of narrow, well-defined interplanetary field depressions. Eleven of these events are associated with electron enhancements, five with significant magnetic field direction changes, and six without. Thus even though such magnetic depressions usually coincide with electron enhancements at energies of ~100 eV, these enhancements cannot always be the result of magnetic reconnection. It seems likely that some events involve local acceleration, possibly the result of reconnection, while others may involve electrons injected onto the field line at a remote point.