Abstract: A lunge line controller (20) which can be easily and conveniently operated by one hand for lunging a horse for training or exercising purposes while avoiding injury to the operator or the animal, includes a housing (22) in which a reel (26) is disposed and pivoted on a shaft (60). The reel includes a cylindrical central hub (96) containing a spring (30). The reel has planar circular flanges (106) that project outwardly from both outer surfaces and includes evenly spaced teeth (112) on the outside of the flanges. The spring connects to the shaft to urge the reel in one direction of rotation. A flexible tape (32) is connected to the reel and extends out of the housing and has a clip (36) at its free end. When in a release position, the spring rotates the reel, thus coiling the tape around the reel until the clip reaches the housing. The latching means (28) comprises an actuation and locking button (38) biased by a spring (132) to an outward position. The button comprises two rectangular portions, i.e.