A computation method is presented which allows a rapid indexing of any unknown spot pattern obtained by back‐reflection or transmission Laue methods. The Cartesian coordinates ofnspots are measured in an orthonormal frame referred to the photographic film. Two spots 1 and 2 separated by a wide angular distanceαmare carefully chosen. Their indices are assumed to be less than 5. The set (E) of all the pairs of planes (h1k1l1) and (h2k2l2) making an angleαclose toαmis then computed. Since the pair of reflecting planes related to spots 1 and 2 belongs to (E), each computed pair of planes is tried, in order to determine the orientation of the crystal and to check whether the coordinates of the (n−2) other spots can be matched to dense planes of indices less than 8. If the uncertainty of the measurements is high or ifnis too low, this method gives the possible orientations for the crystal. Plane indices less than 8 have been identified in cubic, tetragonal and orthorhombic cr