Abstract In this paper, we describe a novel transient electromagnetic borehole technology for reservoir monitoring that has important advantages over existing borehole electromagnetic methods. This work is based on computer simulation of a waterflooded reservoir model that demonstrates the efficacy of this technique for reservoir monitoring. Conventional and enhanced oil recovery (EOR) processes such as waterflooding, steam flooding, and chemical flooding cause key changes in reservoir fluid composition over time. The proposed transient electromagnetic borehole technology can be used for fluid front monitoring and to detect bypassed pay in reservoirs. Existing cross-well borehole electromagnetic technology has shown potential for detecting changes in the reservoir over time by measuring resistivity contrasts. However, it has limitations; most notable being that the measurement is limited to the region between a pair of wells. We show that transient measurements have a distinct advantage over traditional continuous-wave measurements in that different segments of the transient signal can be mapped to different regions of the formation. Furthermore, the measured transient signal has no interference from the transmitter because the transmitter is silent when the formation signal is acquired. This technology eliminates the need for using two separate wells simultaneously, and it has better spatial resolution for the region close to the well. We present several 3-dimensional transient simulation results for a single-well triaxial transmitter-receiver system in a hypothetical waterflooded reservoir. Some of the measured signals demonstrate azimuthal and radial sensitivity to a water front 1,000 ft away. This paper describes transient electromagnetic technology for a single-well borehole reservoir monitoring system that can be implemented with permanent sensors, while cross-well technology needs a multi-frequency multi-spacing transmitter-receiver system along with wireline logging equipment for multiple wells. The 3-dimensional transient electromagnetic computer simulations performed for this work are also an important addition to the knowledgebase of the industry.