The design and development of an infrared lens centering machine is described. The device works in transmission mode so that access is not required to the rear surface of the test component. Although developed for the centration of germanium lenses it works equally in the visible and also with other IR materials, allowing centration accuracies better than 2 arc sec to be achieved. A theoretical analysis is given and an expression for the noise equivalent decentration (NED) is derived. A design example is given followed by a calculation of expected performance. The method of discriminating between front and rear surfaces is described.