This paper presents a new routing scheme called Estimated-TCP-throughput Maximization based Routing (ETR) scheme for mobile ad hoc networks (MANET). Many routing protocols have been proposed to build multi-hop networks in MANET. Most of these protocols select a path based simply on hop metrics, although the shortest path is not always the best path under the influence of radio link quality. We propose that the path should be selected with the maximum end-to-end TCP throughput because most of applications use TCP. In ETR, as a new metric for routing, we introduce an estimated TCP-throughput. A source node measures loss and delay for a path with probing packets periodically. The node estimates maximum TCP throughput from the expression of first approximation with those measured values, and exchanges a path dynamically so that the performance of the using path will be the best of all paths. This paper shows the design and implementation of ETR. We add ETR to Dynamic Source Routing (DSR) protocol in our MANET testbed, and evaluate ETR. In the case of 50% packet loss at DSR layer, ETR improves TCP throughput by 93% than unmodified DSR. ETR can select the path whose TCP throughput is maximum from the multiple paths to a destination.