Microfluidics has shown promise as a new platform for assisted reproduction. To assess the potential of microfluidics for fertilization, we studied sperm and fluid motion in microchannels to better understand the flow characteristics in a microfluidic device, how sperm interacted with this flow, and how sperm–oocyte attachment occurs in the device. There is a threshold fluid velocity where sperm transition from traveling with the fluid to a regime in which the sperm can move independently of the flow. A significant population of sperm remained in the inlet well area. Based on the lack of progressive forward movement, it was presumed that these sperm may have defects. Also of extreme interest was the tendency of sperm to travel along surface contours. These observations provide an improved understanding of sperm motion in microchannels and provide a basis for improved device designs that take advantage of the sperm/flow and sperm/geometry interactions.