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A computer program has been written which determines the multiplicity factors for a given set of X-ray or neutron powder diffraction reflections for crystals of any space group. The value of the multiplicity for each reflection is determined from a look-up table which is indexed by the symmetry type, determined directly from the space-group number, and the reflection type, determined from the Miller indices. There are no restrictions on the choice of indices which are used to specify the reflexions.