In situ Laue analysis during microcompression reveals plasticity in [0 0 1]-oriented, directionally solidified Mo alloy pillars to start with slip on the {1 1 2} < 1 1 1 > system having the highest Schmid factor followed by slip on the (1 1 0) plane containing the same Burgers vector. The results are interpreted in terms of the microstructure analyzed by scanning transmission electron microscopy and 3-D atom probe. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.